The interleukin-22/STAT3 pathway potentiates expression of inducible nitric-oxide synthase in human colon carcinoma cells

Role of TH17 cytokines in the control of colorectal cancer

Immune/inflammatory cells infiltrate almost all human solid tumors and affect all stages of carcinogenesis as they produce different cytokine subsets. The overproduction of T_H17 cytokines marks the early stages of colorectal carcinoma (CRC) and negatively influences the prognosis of CRC patients. Studies with murine models of CRC have delineated the mechanisms by which T_H17 cytokines, notably, interleukin (IL)-17A, IL-17F, IL-21, and IL-22, regulate oncogenesis and tumor progression, paving the way to the development of novel anticancer drugs. In this review article, we discuss experimental data supporting the role of T_H17 cytokines in the modulation of colorectal tumorigenesis.

IL-22 in tissue-protective therapy

IL-22, a member of the IL-10 cytokine family, has recently gained significant attention as a protective agent in murine models of diseases driven by epithelial injury. Like its biochemical and functional sibling IL-10, IL-22 elicits cellular activation primarily by engaging the STAT3 signalling pathway. Exclusively produced by leukocytes, but targeting mostly cells of epithelial origin, IL-22 has been proposed as a specialized cytokine messenger acting between leukocytic and non-leukocytic cell compartments. A lack of response in leukocytes to IL-22 mirrors tightly controlled IL-22 receptor expression and probably explains the apparent lack of instant adverse effects after systemic IL-22 administration to mice. Anti-apoptotic, pro-proliferative and pro-regenerative characteristics the major biological properties of this cytokine. Specifically, application of IL-22 is associated with tissue protection and/or regeneration in murine models of infection/microbe-driven inflammation at host/environment interfaces, ventilator-induced lung injury, pancreatitis and liver damage. Overall, preclinical studies would support therapeutic administration of seemingly well-tolerated recombinant IL-22 for treatment of an array of acute diseases manifested in epithelial tissues. However, the feasibility of prolonged administration of this cytokine is expected to be restricted by the tumourigenic potential of the IL-22/STAT3 axis. IL-22, moreover, apparently displays an inherent context-specific capacity to amplify distinct aspects of autoimmune inflammation. Here, the prospects, expectations and restrictions of IL-22 administration in tissue-protective therapy are discussed.

Expression of interleukin-22/STAT3 signaling pathway in ulcerative colitis and related carcinogenesis

AIM

To investigate the expression of interleukin (IL)-22 and its related proteins in biopsy specimens from patients with ulcerative colitis (UC) and UC-related carcinogenesis.

METHODS

Biopsy specimens were obtained from patients with inactive (n = 10), mild-to-moderately active (n = 30), severely active (n = 34), initial (n = 30), and chronic UC (n = 44), as well as UC patients with dysplasia (n = 10). Specimens from patients without colonic abnormalities (n = 20) served as controls. Chronic colitis in experimental mice was induced by 2.5% dextran sodium sulfate. The expression levels of IL-22, IL-23, IL-22R1 and phosphorylated STAT3 (p-STAT3) were determined by immunohistochemistry. Bcl-2, cyclin D1 and survivin expression was detected by Western blotting.

RESULTS

Patients with active UC had significantly more IL-22, IL-23, IL-22R1 and p-STAT3-positive cells than the patients with inactive UC and normal controls. Furthermore, IL-22 and related proteins were closely related to the severity of the colitis. The expression of IL-22 and IL-22R1 in the tissue of initial UC was stronger than in that of chronic UC, whereas the expression of p-STAT3 was significantly increased in chronic UC tissues. In dysplasia tissues, the expression level of IL-22 and related proteins was higher compared with controls. Mouse colitis model showed that expression of IL-22, IL-22R1 and IL-23 was increased with time, p-STAT3 and the downstream gene were also remarkably upregulated.

CONCLUSION

IL-22/STAT3 signaling pathway may be related to UC and UC-induced carcinogenesis and IL-22 can be used as a biomarker in judging the severity of UC.

Increased Tc22 and Treg/CD8 ratio contribute to aggressive growth of transplant associated squamous cell carcinoma

Immune suppressed organ transplant recipients suffer increased morbidity and mortality from primary cutaneous SCC. We studied tumor microenvironment in transplant-associated SCC (TSCC), immune-competent SCC and normal skin by IHC, IF and RT-PCR on surgical discard. We determined T cell polarization in TSCC and SCC by intracellular cytokine staining of T cell crawl outs from human skin explants. We studied the effects of IL-22, an inducer of keratinocyte proliferation, on SCC proliferation in vitro. SCC and TSCC are both associated with significantly higher numbers of CD3(+) and CD8(+) T cells compared to normal skin. TSCC showed a higher proportion of Foxp3(+) T regs to CD8(+) T cells compared to SCC and a lower percentage of IFN-γ producing CD4(+) T cells. TSCC, however, had a higher percentage of IL-22 producing CD8(+) T cells compared to SCC. TSCC showed more diffuse Ki67 and IL-22 receptor (IL-22R) expression by IHC. IL-22 induced SCC proliferation in vitro despite serum starvation. Diminished cytotoxic T cell function in TSCC due to decreased CD8/T-reg ratio may permit tumor progression. Increased IL-22 and IL-22R expression could accelerate tumor growth in transplant patients. IL-22 may be an attractive candidate for targeted therapy of SCC without endangering allograft survival.

Innate lymphoid cells sustain colon cancer through production of interleukin-22 in a mouse model

Patients with inflammatory bowel disease (IBD) have an increased risk of colon cancer. However, the immune cells and cytokines that mediate the transition from intestinal inflammation to cancer are poorly understood. We show that bacteria-induced colon cancer is accompanied by differential accumulation of IL-17(+)IL-22(+) colonic innate lymphoid cells (cILCs), which are phenotypically distinct from LTi and NK-22 cells, and that their depletion in mice with dysplastic inflammation blocks the development of invasive colon cancer. Analysis of the functional role of distinct Type 17 cytokines shows that although blockade of IL-17 inhibits some parameters of intestinal inflammation, reduction in dysplasia and colorectal cancer (CRC) requires neutralization of IL-22 indicating a unique role for IL-22 in the maintenance of cancer in this model. Mechanistic analyses showed that IL-22 selectively acts on epithelial cells to induce Stat3 phosphorylation and proliferation. Importantly, we could detect IL-22(+)CD3(+) and IL-22(+)CD3(−) cells in human CRC. Our results describe a new activity of IL-22 in the colon as a nonredundant mediator of the inflammatory cascade required for perpetuation of CRC, highlighting the IL-22 axis as a novel therapeutic target in colon cancer.

IL-22 exacerbates the severity of CVB3-induced acute viral myocarditis in IL-17A-deficient mice

Interleukin (IL)-22 has either proinflammatory or tissue‑protective properties, depending on the nature of the affected tissue and the local cytokine milieu, including the presence or absence of IL-17A co-expression. We have previously demonstrated that IL-22 has critical anti-inflammatory and antiviral roles in mice with coxsackievirus B3 (CVB3)‑induced acute viral myocarditis (AVMC) in the presence of IL-17A. However, whether IL-17A determines the function of IL-22 in AVMC remains unknown. Therefore, the present study, in continuation of our previous investigations, aimed to determine whether IL-22 plays a distinctly different role in the absence of IL-17A in AVMC by using IL-17A-deficient mice. Results demonstrated that the neutralization of IL-22 in IL-17A‑deficient mice alleviated the severity of myocarditis. This was demonstrated by the lower pathological scores of heart sections and ratios of heart weight/body weight (HW/BW), reduced production of activator of transcription 3 (STAT3) and proinflammatory cytokines TNF-α and IL-6, followed by increased viral replication and decreased levels of the antiviral cytokine IFN-γ. Furthermore, the correlation between cardiac CVB3 RNA and IL-22 mRNA or IFN-γ mRNA was negative. In conclusion, IL-22 exacerbated the severity of AVMC and restrained viral replication in the absence of IL-17A. Spleen lymphocytes cultured with recombinant IL-17 (rIL-17) increased the production of IL-22. Combined with our previous data, these results indicate that IL-17A is not involved in regulating the antiviral role, however, may mediate the tissue-protective versus pathogenic properties of IL-22 in CVB3-induced AVMC in mice.

Pro-Inflammatory Signaling by IL-10 and IL-22: Bad Habit Stirred Up by Interferons?

Interleukin (IL)-10 and IL-22 are key members of the IL-10 cytokine family that share characteristic properties such as defined structural features, usage of IL-10R2 as one receptor chain, and activation of signal transducer and activator of transcription (STAT)-3 as dominant signaling mode. IL-10, formerly known as cytokine synthesis inhibitory factor, is key to deactivation of monocytes/macrophages and dendritic cells. Accordingly, pre-clinical studies document its anti-inflammatory capacity. However, the outcome of clinical trials assessing the therapeutic potential of IL-10 in prototypic inflammatory disorders has been disappointing. In contrast to IL-10, IL-22 acts primarily on non-leukocytic cells, in particular epithelial cells of intestine, skin, liver, and lung. STAT3-driven proliferation, anti-apoptosis, and anti-microbial tissue protection is regarded a principal function of IL-22 at host/environment interfaces. In this hypothesis article, hidden/underappreciated pro-inflammatory characteristics of IL-10 and IL-22 are outlined and related to cellular priming by type I interferon. It is tempting to speculate that an inherent inflammatory potential of IL-10 and IL-22 confines their usage in tissue protective therapy and beyond that determines in some patients efficacy of type I interferon treatment.

IFNα converts IL-22 into a cytokine efficiently activating STAT1 and its downstream targets

Besides their antiviral activity, type I Interferons (IFN) display context-specific immunomodulation. In contrast to long-known IFNα/β, Interleukin (IL)-22 is an anti-bacterial, largely tissue protective cytokine that recently gained attention. Herein, cellular IFNα/IL-22 interactions are investigated. We report that pre-conditioning of epithelial cells with IFNα initiated dramatic changes in IL-22 signaling normally dominated by signal transducer and activator of transcription (STAT)-3. Specifically, by using human DLD1 colon epithelial/carcinoma cells we demonstrate that, upon IFNα, IL-22 converts into a cytokine robustly activating STAT1 and its downstream pro-inflammatory targets CXCL9, CXCL10, and inducible nitric oxide synthase (iNOS). Accordingly, only after IFNα pre-incubation was IL-22-induced STAT1 binding to the CXCL10 promoter detectable. Using the viral mimic polyinosinic:polycytidylic acid and the IFNα/β antagonist B18R we furthermore demonstrate the capability of endogenous IFN to promote IL-22-induced STAT1 activation and expression of CXCL10. IL-22-induced STAT1 activation subsequent to IFNα priming became likewise apparent in human Caco2 colon epithelial/carcinoma cells, HepG2 hepatoma cells, and primary keratinocytes. Current observations may relate to characteristics of IFNα/β in clinical therapy and expose margins of tissue protection by IL-22 application.

STAT3 signal transduction through interleukin-22 in oral squamous cell carcinoma

Interleukin (IL)-22 is a member of the IL-10 family. Its main targets are epithelial cells, not immune cells. We examined IL-22 signal transduction in oral squamous cell carcinoma (OSCC) cells. Immunohistochemical staining revealed that IL-22R was expressed more highly in OSCC compared to normal regions. An IL-22R signal was also observed in metastatic OSCC cells in the lymph node. RT-PCR showed that the human OSCC cell lines MISK81-5, HSC-3, HSC-4, SAS and SQUU-B expressed IL-22 receptor chains. Immunoblotting showed that IL-22 induced a transient tyrosine phosphorylation of STAT3 (pY705-STAT3) in MISK81-5 cells. The change in the serine phosphorylation of STAT3 was subtle during the examination periods. Simultaneously, pY705-STAT3 activation in HSC-3 cells was undetectable after IL-22 stimulation. Immunocytochemistry demonstrated that IL-22 induced the translocation of phosphorylated STAT3 into the nucleus of MISK81-5 cells. IL-22 temporarily upregulated the expression of anti-apoptotic and mitogenic genes such as Bcl-x, survivin and c-Myc, as well as SOCS3. IL-22 transiently activated ERK1/2 and induced a delayed phosphorylation of p38 MAP kinase, but negligibly involved the activation of NF-κB in MISK81-5 cells. MISK81-5 and SQUU-B cells treated with IL-22 showed mild cellular proliferation. MISK81-5, HSC-4 and SAS cells treated with IL-22 downregulated the keratinocyte differentiation-related genes compared with unstimulated cells. Conversely, STAT3 suppression by STAT3 siRNA strongly disrupted the downregulation of these genes by IL-22, but it did not significantly affect the activation of ERK1/2 by IL-22. The OSCC cells used in this study upregulated the expression of SERPINB3/4 (SCCA1/2), well-known SCC markers, following treatment with IL-22. These results indicate that IL-22 differentially activates the STAT3 signaling system depending on the type of OSCC. IL-22 may therefore play a role in tumor growth, cell differentiation and progression through STAT3-dependent and -independent pathways.

Interleukin-22 predicts severity and death in advanced liver cirrhosis: a prospective cohort study

BACKGROUND

Interleukin-22 (IL-22), recently identified as a crucial parameter of pathology in experimental liver damage, may determine survival in clinical end-stage liver disease. Systematic analysis of serum IL-22 in relation to morbidity and mortality of patients with advanced liver cirrhosis has not been performed so far.

METHODS

This is a prospective cohort study including 120 liver cirrhosis patients and 40 healthy donors to analyze systemic levels of IL-22 in relation to survival and hepatic complications.

RESULTS

A total of 71% of patients displayed liver cirrhosis-related complications at study inclusion. A total of 23% of the patients died during a mean follow-up of 196 ± 165 days. Systemic IL-22 was detectable in 74% of patients but only in 10% of healthy donors (P < 0.001). Elevated levels of IL-22 were associated with ascites (P = 0.006), hepatorenal syndrome (P < 0.0001), and spontaneous bacterial peritonitis (P = 0.001). Patients with elevated IL-22 (>18 pg/ml, n = 57) showed significantly reduced survival compared to patients with regular (≤18 pg/ml) levels of IL-22 (321 days versus 526 days, P = 0.003). Other factors associated with reduced overall survival were high CRP (≥2.9 mg/dl, P = 0.005, hazard ratio (HR) 0.314, confidence interval (CI) (0.141 to 0.702)), elevated serum creatinine (P = 0.05, HR 0.453, CI (0.203 to 1.012)), presence of liver-related complications (P = 0.028, HR 0.258, CI (0.077 to 0.862)), model of end stage liver disease (MELD) score ≥20 (P = 0.017, HR 0.364, CI (0.159 to 0.835)) and age (P = 0.011, HR 0.955, CI (0.922 to 0.989)). Adjusted multivariate Cox proportional-hazards analysis identified elevated systemic IL-22 levels as independent predictors of reduced survival (P = 0.007, HR 0.218, CI (0.072 to 0.662)).

CONCLUSIONS

In patients with liver cirrhosis, elevated systemic IL-22 levels are predictive for reduced survival independently from age, liver-related complications, CRP, creatinine and the MELD score. Thus, processes that lead to a rise in systemic interleukin-22 may be relevant for prognosis of advanced liver cirrhosis.

IL-27 Regulates IL-18 binding protein in skin resident cells

IL-18 is an important mediator involved in chronic inflammatory conditions such as cutaneous lupus erythematosus, psoriasis and chronic eczema. An imbalance between IL-18 and its endogenous antagonist IL-18 binding protein (BP) may account for increased IL-18 activity. IL-27 is a cytokine with dual function displaying pro- and anti-inflammatory properties. Here we provide evidence for a yet not described anti-inflammatory mode of action on skin resident cells. Human keratinocytes and surprisingly also fibroblasts (which do not produce any IL-18) show a robust, dose-dependent and highly inducible mRNA expression and secretion of IL-18BP upon IL-27 stimulation. Other IL-12 family members failed to induce IL-18BP. The production of IL-18BP peaked between 48-72 h after stimulation and was sustained for up to 96 h. Investigation of the signalling pathway showed that IL-27 activates STAT1 in human keratinocytes and that a proximal GAS site at the IL-18BP promoter is of importance for the functional activity of IL-27. The data are in support of a significant anti-inflammatory effect of IL-27 on skin resident cells. An important novel property of IL-27 in skin pathobiology may be to counter-regulate IL-18 activities by acting on keratinocytes and importantly also on dermal fibroblasts.

SOCS3 in immune regulation of inflammatory bowel disease and inflammatory bowel disease-related cancer

Inflammatory bowel disease (IBD) has unclear pathogenesis and it is related to the increasing risk of developing colorectal cancer (CRC). Recent studies have uncovered the molecular mechanism of intracellular signaling pathways of inflammatory cytokines such as tumor necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-6. The major transcription factors including STAT3 have been shown to play a major role in transmitting inflammatory cytokine signals to the nucleus. The suppressors of cytokine signaling (SOCS) 3 protein is the key physiological regulators of cytokine-mediated STAT3 signaling. As such it influences the development of inflammatory and malignant disorders like this associated with IBD. Here we review the complex function of SOCS3 in innate and adaptive immunity, different cell types (macrophages, neutrophils, dendritic cells, B cells, T cells and intestinal epithelial cells) and the role of SOCS3 on the pathogenesis of inflammatory bowel disease (IBD) and IBD-related cancer. Finally, we explore how this knowledge may open novel avenues for the rational treatment of IBD and IBD-related cancer.

Mechanisms of rapid induction of interleukin-22 in activated T cells and its modulation by cyclosporin a

IL-22 is an immunoregulatory cytokine displaying pathological functions in models of autoimmunity like experimental psoriasis. Understanding molecular mechanisms driving IL-22, together with knowledge on the capacity of current immunosuppressive drugs to target this process, may open an avenue to novel therapeutic options. Here, we sought to characterize regulation of human IL22 gene expression with focus on the established model of Jurkat T cells. Moreover, effects of the prototypic immunosuppressant cyclosporin A (CsA) were investigated. We report that IL-22 induction by TPA/A23187 (T/A) or αCD3 is inhibited by CsA or related FK506. Similar data were obtained with peripheral blood mononuclear cells or purified CD3(+) T cells. IL22 promoter analysis (-1074 to +156 bp) revealed a role of an NF-AT (-95/-91 nt) and a CREB (-194/-190 nt) binding site for gene induction. Indeed, binding of CREB and NF-ATc2, but not c-Rel, under the influence of T/A to those elements could be proven by ChIP. Because CsA has the capability to impair IκB kinase (IKK) complex activation, the IKKα/β inhibitor IKKVII was evaluated. IKKVII likewise reduced IL-22 induction in Jurkat cells and peripheral blood mononuclear cells. Interestingly, transfection of Jurkat cells with siRNA directed against IKKα impaired IL22 gene expression. Data presented suggest that NF-AT, CREB, and IKKα contribute to rapid IL22 gene induction. In particular the crucial role of NF-AT detected herein may form the basis of direct action of CsA on IL-22 expression by T cells, which may contribute to therapeutic efficacy of the drug in autoimmunity.

IL-22 is produced by innate lymphoid cells and limits inflammation in allergic airway disease

Interleukin (IL)-22 is an effector cytokine, which acts primarily on epithelial cells in the skin, gut, liver and lung. Both pro- and anti-inflammatory properties have been reported for IL-22 depending on the tissue and disease model. In a murine model of allergic airway inflammation, we found that IL-22 is predominantly produced by innate lymphoid cells in the inflamed lungs, rather than TH cells. To determine the impact of IL-22 on airway inflammation, we used allergen-sensitized IL-22-deficient mice and found that they suffer from significantly higher airway hyperreactivity upon airway challenge. IL-22-deficiency led to increased eosinophil infiltration lymphocyte invasion and production of CCL17 (TARC), IL-5 and IL-13 in the lung. Mice treated with IL-22 before antigen challenge displayed reduced expression of CCL17 and IL-13 and significant amelioration of airway constriction and inflammation. We conclude that innate IL-22 limits airway inflammation, tissue damage and clinical decline in allergic lung disease.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

Interleukin-22 suppresses the growth of A498 renal cell carcinoma cells via regulation of STAT1 pathway

BACKGROUND

Renal cell carcinoma (RCC) is one of the most common kidney cancers and is highly resistant to chemotherapy. Accumulating evidence suggests that interleukin-22 (IL-22) may mediate host defense against varietal pathogens as a proinflammatory and anti-inflammatory cytokine. The purpose of this study is to assess the inhibitory effects of IL-22 on human RCC cell line A498 and to investigate the possible mechanisms underlying the anti-tumor effects of this cytokine.

METHODOLOGY

A498 cells, a RCC cell line, were used to assess the inhibitory growth effects of IL-22 using the MTT assay and flow cytometric analysis in vitro. BALB/C nude mice bearing A498 cell xenografts were used to examine the antitumor efficacy of IL-22 in vivo. Western blotting assay was performed to detect the regulation of the intracellular signaling pathway of IL-22.

PRINCIPAL FINDINGS

We found that IL-22 suppressed the growth of A498 cells in a dose-dependent manner and inhibited the growth of A498 xenografts. We also observed that IL-22 produced a dose-dependent inhibitory effect on A498 cells that involved the induction of G2/M cell cycle arrest without cell apoptosis. Moreover, we showed that the phosphorylation of STAT1 was increased and the phosphorylation of ERK1/2 was attenuated in A498 cells exposed to IL-22. The growth inhibition of A498 cells was partially revised after IL-22 treatment as the expression of STAT1 was knocked down. And inflammatory cytokines, interferon-α and tumor necrosis factor-α (TNF-α) were barely involved in the suppression of A498 cell xenografts treated with IL-22.

CONCLUSIONS

IL-22 dose-dependently suppresses RCC cell line A498 cells in vitro and induces growth inhibition of A498 cell-bearing mouse xenografts. These results suggest that the anti-RCC effects of IL-22 are at least partially mediated through regulation of STAT1 signaling pathways and G2/M cell cycle arrest, rather than by inducing apoptosis and inflammatory cytokines.

Interferon-γ and nitric oxide production during Behçet uveitis: immunomodulatory effect of interleukin-10

Uveitis is one of the major manifestations of Behçet Disease, a systemic inflammatory vasculitis. Our aim is to investigate in vivo and in vitro production of interferon (IFN)-γ and nitric oxide (NO) during Behçet uveitis (BU). Moreover, we evaluated the implication of IFN-γ and interleukin (IL)-10 in the regulation of NO production in vitro. Cytokines' concentrations were measured by ELISA, and NO levels were assessed by modified Griess's method. Our results showed that patients with active disease had significant elevation of IFN-γ and NO concentrations in both plasma and peripheral blood mononuclear cell culture supernatants compared with controls (P<0.01) or to patients with inactive disease (P<0.05). Further, IFN-γ induced significantly higher production of NO in cell culture supernatants, whereas IL-10 significantly reduced it (P<0.05). In conclusion, the elevated levels of IFN-γ in vivo and in vitro in patients with BU reflect the implication of this cytokine in the disease physiopathology. These results suggest that IFN-γ, through the induction of NO synthase 2 and the production of NO, is implicated in the genesis of the inflammatory process during active BU; whereas IL-10 seems to have protective properties.

Interleukin-21 induces the differentiation of human Tc22 cells via phosphorylation of signal transducers and activators of transcription

Interleukin-21 (IL-21) exerts critical functions in T helper type 17 (Th17) cell development. However, the effect of IL-21 on the differentiation of IL-22-producing T cells is not clear. Here we showed that IL-21 induced the differentiation of human naive CD8(+) T cells into Tc22 cells without the expression of IL-17. The addition of transforming growth factor-β inhibited the production of IL-22 but induced the production of IL-17. Both IL-15 and IL-2 induced interferon-γ production but did not induce differentiation of Tc22, which suggests that common γ-chain signals are not specific to promote IL-22 synthesis. The IL-21 induced naive CD8(+) T cells to produce IL-22 in greater amounts than memory CD8(+) T cells. In addition, we demonstrated that IL-21 promoted the proliferation and increased the expression of IL-21 receptors on activated naive CD8(+) T cells. Furthermore, IL-21 increased the expression of granzyme B molecules. Analysis of molecular mechanisms indicated that IL-21 induced phosphorylation of signal transducers and activators of transcription 1, 3 and 5 in CD8(+) T cells. Overall, our data indicated that IL-21, an effector cytokine produced by CD4(+) T cells, might mediate the cross-talk between CD4(+) and CD8(+) T cells through the production of IL-22.

Inducible NO synthase and antibacterial host defence in times of Th17/Th22/T22 immunity

During the last two decades nitric oxide (NO) produced by inducible NO synthase (iNOS or NOS2) has been characterized as immunoregulatory and antimicrobial principle displaying the potential to determine course of disease in a range of infections. Being an enzyme primarily regulated on expressional level, cytokine-driven iNOS appears to be connected in particular with activation of Th1-type immunity. However, with the recent advent of additional, partly overlapping CD4(+) T cell effector subsets, namely Th17 and Th22 cells, a further layer of complexity has been added to immunoregulatory networks determining inflammatory gene expression in the context of microbial infections. Here, we review current knowledge on activation of iNOS function by interleukin (IL)-17 and IL-22 with focus on Th17/Th22-directed antibacterial immunity.

ΔNp63α/IRF6 interplay activates NOS2 transcription and induces autophagy upon tobacco exposure

Tobacco-induced oxidative stress leads to chronic inflammation and is implicated in the development of many human epithelial cancers, including head and neck cancer. Cigarette smoke exposure was shown to induce the expression of the ΔNp63α and nitric oxide synthase (NOS)-2 in head and neck squamous cell carcinoma cells and immortalized oral keratinocytes. The NOS2 promoter was found to contain various cognate sequences for several transcription factors including interferon regulatory factor (IRF)-6 and p63, which were shown in vivo binding to the NOS2 promoter in response to smoke exposure. Small interfering (si)-RNAs against both ΔNp63α and IRF6 decreased the induction of NOS2 promoter-driven reporter luciferase activity and were shown to inhibit NOS2 activity. Furthermore, both mainstream (MSE) and sidestream (SSE) smoking extracts induced changes in expression of autophagic marker, LC3B, while siRNA against ΔNp63α, IRF6 and NOS2 modulated these autophagic changes. Overall, these data support the notion that ΔNp63α/IRF6 interplay regulates NOS2 transcription, thereby underlying the autophagic-related cancer cell response to tobacco exposure.

Interleukin 22 signaling promotes cell growth in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a specific type of aggressive B-cell non-Hodgkin lymphoma. We recently found that IL-22RA1, one of the two subunits of the interleukin 22 (IL-22) receptor, is expressed in MCL cell lines but not benign lymphocytes. In view of normal functions of IL-22 signaling, we hypothesized that the aberrant expression of IL-22RA1 may contribute to the deregulation of various cell signaling pathways, thereby promoting cell growth in MCL. In this study, we first demonstrated the expression of IL-22RA1 in all three MCL cell lines and eight frozen tumors examined using reverse transcription-polymerase chain reaction and Western blot analysis. In support of the concept that IL-22 signaling is biologically important in MCL, we found that MCL cells treated with recombinant IL-22 had a significant increase in cell growth that was associated with STAT3 activation. To investigate the mechanism underlying the aberrant expression of IL-22RA1, we analyzed the gene promoter of IL-22RA1, and we found multiple binding sites for NF-κB, a transcriptional factor strongly implicated in the pathogenesis of MCL. Pharmacologic inhibition of NF-κB resulted in a substantial reduction in the level of IL-22RA1 protein expression in MCL cells. To conclude, IL-22RA is aberrantly expressed in MCL, and we have provided evidence that IL-22 signaling contributes to the pathogenesis of MCL.

Darbepoetin-mediated cardioprotection after myocardial infarction involves multiple mechanisms independent of erythropoietin receptor-common beta-chain heteroreceptor

BACKGROUND AND PURPOSE

Darbepoetin, a long-acting erythropoietin derivative, attenuates cardiomyocyte apoptosis and improves short-term (3 days) cardiac function, but the mechanisms responsible are unknown. We investigated potential mechanisms by which darbepoetin exerts cardioprotection following myocardial infarction in mice and the significance of the erythropoietin receptor (EPOR)-common beta-chain (c-beta-chain) heteroreceptor.

EXPERIMENTAL APPROACH

Mice underwent 60 min coronary occlusion followed by treatment with vehicle or a single dose of darbepoetin. Effects on gene expression, apoptosis and neutrophil accumulation in infarcted left ventricle were assessed 24 h later. Cardiac function, effects on vascularization and fibrosis were assessed 28 days later. The significance of EPOR-c-beta-chain heteroreceptor was examined 28 days after infarction using mice deficient in c-beta-chain.

KEY RESULTS

Twenty-four hours after darbepoetin, mRNAs encoding haeme oxygenase-1 (HO-1), iNOS and brain natriuretic peptide (BNP) were markedly elevated only in infarcted regions, and the frequency of apoptotic cells attenuated. Inflammation was also attenuated with reductions in neutrophil numbers. Darbepoetin also elevated mRNAs encoding angiogenic factors: placental growth factor, monocyte chemoattractant protein-1 and interleukin-1beta. Twenty-eight days after treatment, CD31+ vessels in the infarct zone doubled and fibrosis reduced. Cardiac haemodynamics were improved. Darbepoetin also improved cardiac haemodynamics in c-beta-chain-deficient mice, increased HO-1 and iNOS expression and vessel numbers and attenuated fibrosis.

CONCLUSIONS AND IMPLICATIONS

Darbepoetin stimulates expression of haeme oxygenase, iNOS, BNP and angiogenic factors specifically in infarcted left ventricle that attenuates inflammation, apoptosis and fibrosis; elevate vessel numbers; and improve cardiac function. The EPOR-c-beta-chain heteroreceptor is not essential for these effects.

Early production of IL-22 but not IL-17 by peripheral blood mononuclear cells exposed to live Borrelia burgdorferi: the role of monocytes and interleukin-1

If insufficiently treated, Lyme borreliosis can evolve into an inflammatory disorder affecting skin, joints, and the CNS. Early innate immunity may determine host responses targeting infection. Thus, we sought to characterize the immediate cytokine storm associated with exposure of PBMC to moderate levels of live Borrelia burgdorferi. Since Th17 cytokines are connected to host defense against extracellular bacteria, we focused on interleukin (IL)-17 and IL-22. Here, we report that, despite induction of inflammatory cytokines including IL-23, IL-17 remained barely detectable in response to B. burgdorferi. In contrast, T cell-dependent expression of IL-22 became evident within 10 h of exposure to the spirochetes. This dichotomy was unrelated to interferon-γ but to a large part dependent on caspase-1 and IL-1 bioactivity derived from monocytes. In fact, IL-1β as a single stimulus induced IL-22 but not IL-17. Neutrophils display antibacterial activity against B. burgdorferi, particularly when opsonized by antibodies. Since neutrophilic inflammation, indicative of IL-17 bioactivity, is scarcely observed in Erythema migrans, a manifestation of skin inflammation after infection, protective and antibacterial properties of IL-22 may close this gap and serve essential functions in the initial phase of spirochete infection.

Interleukin-22 detected in patients with abdominal sepsis

Interleukin 22 (IL-22) is a TH17-like cytokine known to specifically activate epithelial cells, thereby strengthening immune defense at host/environment interfaces. Animal studies suggest that IL-22 may play a crucial role in clinical sepsis. However, little is known about IL-22 in sepsis patients. In a single-center university hospital setting, serum IL-22 levels were assessed in 16 patients with the diagnosis of abdominal sepsis, 16 patients who have undergone elective major abdominal surgery without the diagnosis of sepsis, and 21 healthy volunteers. In accordance with current knowledge, we observed enhanced levels of IL-6 and IL-10 in serum specimens of sepsis patients compared with surgical control patients. Here, we report, for the first time, a modest but significant elevation of serum IL-22 detectable in abdominal sepsis patients (P G 0.001). Median serum concentrations of IL-22 were 111.8 pg/mL, 3.4 or 2.0 pg/mL, and 9.3 pg/mL for abdominal sepsis patients, surgical control patients (presurgery or postsurgery), and healthy volunteers,respectively. Interleukin 22 produced in the course of abdominal sepsis may contribute to host defense and stabilization of mucosal barrier functions under conditions of systemic infection.

Th17 cells, HIV and the gut mucosal barrier

PURPOSE OF REVIEW

We will present recent studies on a subset of CD4 T helper cells, Th17 cells, that appears to be critical for regulating gut mucosal immune responses against extracellular microbial pathogens and may serve as a link between innate and adaptive immune responses. Implications of the loss of Th17 CD4 T cells in HIV infection will be discussed in relation to the chronic immune activation and HIV pathogenesis.

RECENT FINDINGS

Severe depletion of CD4 T cells occurs in the gut mucosa during primary HIV and simian immunodeficiency virus infections. A pronounced loss of mucosal Th17 CD4 T cells in the simian immunodeficiency virus-infected rhesus macaque model of AIDS is linked to impaired immune responses in the gut mucosa to an enteric pathogen, Salmonella typhimurium, leading to the lack of local control of the pathogen and its translocation. Recovery of the gut mucosal immune system during highly active antiretroviral therapy is slow and incomplete compared with the peripheral blood compartment. Recent studies suggest that the replenishment of Th17 CD4 T cells in the gut mucosa during highly active antiretroviral therapy, or during nonpathogenic simian immunodeficiency virus infections in the nonhuman primate models, correlates with better restoration and function of the gut mucosal immune system.

SUMMARY

A better understanding of the role of Th17 CD4 cells in the generation of mucosal immune responses to enteric pathogens and maintenance of the intestinal epithelial integrity in HIV-infected patients will help in the development of novel strategies to modulate and enhance mucosal immune system and its function.

Interleukin-22 genetic polymorphisms and risk of colon cancer

Interleukin-22 (IL-22) is a member of the IL-10 family of anti-inflammatory cytokines that mediates epithelial immunity. IL-22 expression is enhanced in inflamed colon mucosa in individuals with inflammatory bowel disease. We carried out an association study to examine the hypothesis that common variation in the IL-22 gene is associated with risk of colon cancer. Seven tagging SNPs were genotyped in 561 colon cancer cases and 722 population controls. Information on lifestyle risk factors was collected via a self-administered questionnaire. The rs1179251 SNP conferred an estimated odds ratio (OR) of 1.46 (95% CI = 1.04-2.05) and 2.10 (95% CI = 0.66-6.66), respectively, for those heterozygous and homozygous for the G variant (p (additive) = 0.013) after adjustment for age, gender, and race; the OR assuming a dominant model was 1.50 (95% CI = 1.05-2.08, p (dominant) = 0.016). No other SNP was statistically significantly associated with colon cancer risk. Haplotype analysis found that one haplotype containing the rs1179251 G allele gave an estimated 52% increase in risk of colon cancer for individuals with at least one copy (OR = 1.52, 95% CI = 1.12-2.06, p = 0.0073). Our findings suggest that the rs1179251 SNP in IL-22 is associated with risk of colon cancer.

The role of NF-κB and PPARγ in experimentally induced colorectal cancer and chemoprevention by cyclooxygenase-2 inhibitors

Initiation of malignancy is dependent upon the basic ratio of cell proliferation and apoptosis. Many molecular proteins and pathways are responsible for the imbalance of proliferation and apoptosis ratio. For example, Akt is a key biomolecule which regulates the cell survival signals via various downstream pathways. One of those pathways is nuclear factor-κB activation which also regulates many downstream pathways that are essential for cell survival. Along with these anti-apoptotic pathways, cells do have a parallel mechanism to prevent malignancy with the help of the ligand-induced nuclear receptors, e.g., peroxisome proliferator-activated receptor gamma (PPARγ). PPARγ has been found to be expressed in many cancer cell types and reported to be a pro-apoptotic transcription factor. The study aimed to observe the ability of two cyclooxygenase-dependent non-steroidal anti-inflammatory drugs (NSAIDs) in the prevention of experimentally induced early neoplasm of colon via NF-κB and PPARγ pathways. Early stages of colorectal cancer were produced in rats with 1,2-dimethylhydrazine dihydrochloride. Western blotting and immunohistochemistry were performed along with morphological and histological analysis. According to the expression levels of NF-κB and PPARγ in the cell nuclei, it is observed that NSAIDs may prevent colorectal cancer in the early stages by a concomitant down-regulation of NF-κB and up-regulation of PPARγ. COX-independent mechanism of anti-carcinogenesis was observed by COX-dependent NSAIDs in colorectal cancer.

Stat3: linking inflammation to epithelial cancer - more than a "gut" feeling?

Inflammation is an important environmental factor that promotes tumourigenesis and the progression of established cancerous lesions, and recent studies have started to dissect the mechanisms linking the two pathologies. These inflammatory and infectious conditions trigger immune and stromal cell release of soluble mediators which facilitate survival and proliferation of tumour cells in a paracrine manner. In addition, (epi-)genetic mutations affecting oncogenes, tumour-suppressor genes, chromosomal rearrangements and amplifications trigger the release of inflammatory mediators within the tumour microenvironment to promote neoplastic growth in an autocrine manner. These two pathways converge in tumour cells and result in activation of the latent signal transducer and activator of transcription 3 (Stat3) which mediates a transcriptional response favouring survival, proliferation and angiogenesis. The abundance of cytokines that activate Stat3 within the tumour microenvironment, which comprises of members of the interleukin (IL) IL6, IL10 and IL17/23 families, underpins a signaling network that simultaneously promotes the growth of neoplastic epithelium, fuels inflammation and suppresses the host's anti-tumour immune response. Accordingly, aberrant and persistent Stat3 activation is a frequent observation in human cancers of epithelial origin and is often associated with poor outcome.

Here we summarize insights gained from mice harbouring mutations in components of the Stat3 signaling cascade and in particular of gp130, the shared receptor for the IL6 family of cytokines. We focus on the various feed-back and feed-forward loops in which Stat3 provides the signaling node in cells of the tumour and its microenvironment thereby functionally linking excessive inflammation to neoplastic growth. Although these observations are particularly pertinent to gastrointestinal tumours, we suggest that the tumour's addiction to persistent Stat3 activation is likely to also impact on other epithelial cell-derived cancers. These insights provide clues to the judicious interference of the gp130/Stat3 signaling cascade in therapeutically targeting cancer.

Regulation of the expression of inducible nitric oxide synthase

Nitric oxide (NO) generated by the inducible isoform of nitric oxide synthase (iNOS) is involved in complex immunomodulatory and antitumoral mechanisms and has been described to have multiple beneficial microbicidal, antiviral and antiparasital effects. However, dysfunctional induction of iNOS expression seems to be involved in the pathophysiology of several human diseases. Therefore iNOS has to be regulated very tightly. Modulation of expression, on both the transcriptional and post-transcriptional level, is the major regulation mechanism for iNOS. Pathways resulting in the induction of iNOS expression vary in different cells or species. Activation of the transcription factors NF-kappaB and STAT-1alpha and thereby activation of the iNOS promoter seems to be an essential step for the iNOS induction in most human cells. However, at least in the human system, also post-transcriptional mechanisms involving a complex network of RNA-binding proteins build up by AUF1, HuR, KSRP, PTB and TTP is critically involved in the regulation of iNOS expression. Recent data also implicate regulation of iNOS expression by non-coding RNAs (ncRNAs).

Expression of IL-10 family cytokines in rheumatoid arthritis: elevated levels of IL-19 in the joints

OBJECTIVES

Interleukin (IL)-10 functions as an anti-inflammatory cytokine in rheumatoid arthritis (RA). New IL-10 family cytokines IL-19, IL-20, IL-22, IL-24, and IL-26 have recently been discovered. Information concerning the expression and function of these cytokines in autoimmune diseases is currently limited. The aim of this study was to investigate their expression in RA.

METHODS

mRNA levels of the cytokines were studied using quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Peripheral blood (PB) and synovial fluid (SF) mononuclear cells (MCs), purified T cells, and monocytes/macrophages from RA patients and healthy volunteers, and synovial tissues from patients with RA or osteoarthritis (OA), were examined. The expression of IL-19 protein in T cells and monocytes/macrophages was studied by flow cytometry.

RESULTS

IL-10 and IL-19 mRNA levels were significantly elevated in SFMCs from patients with RA compared with PBMCs from RA patients or healthy volunteers. IL-20 and IL-22 mRNA levels were also upregulated in RA SFMCs but their level of expression was lower than that of IL-10 or IL-19. Importantly, synovial tissue IL-19 levels in RA were increased when compared with OA. IL-19 expression was upregulated in both T cells and macrophages derived from patients with RA. IL-1beta increased IL-19 levels in PBMCs, suggesting that elevated levels of IL-1 in RA joints may contribute to upregulated IL-19 expression.

CONCLUSIONS

The majority of the IL-10 family cytokines are expressed in RA. IL-19 demonstrated the highest expression in rheumatoid joints, and could thus be involved in the regulation of synovial inflammation in RA.

Involvement of the IL-22/REG Ialpha axis in ulcerative colitis

The Regenerating gene (REG) Ialpha protein, a trophic and/or anti-apoptotic factor, is important in the pathophysiology of gastrointestinal inflammation. Interleukin (IL)-22 is a recently identified cytokine that is suggested to have pivotal roles in inflammatory bowel diseases. We therefore investigated the involvement of the IL-22/REG Ialpha axis and examined the mechanism of regulation of REG Ialpha expression by IL-22 stimulation in ulcerative colitis (UC) mucosa. Expression of IL-22, IL-22 receptor 1 (IL-22R1), and REG Ialpha in UC mucosa was analyzed by real-time RT-PCR and immunohistochemistry. The effects of IL-22 on REG Ialpha protein expression were examined using a small-interfering RNA for STAT3, an MAPK inhibitor or a PI3K inhibitor. The element responsible for IL-22-induced REG Ialpha promoter activation was determined by a promoter deletion and electrophoretic mobility shift assay. The expression of IL-22 was enhanced in infiltrating inflammatory cells, and that of IL-22R1 and REG Ialpha was concurrently enhanced in the inflamed epithelium in UC mucosa. The levels of REG Ialpha and IL-22 mRNA expression were strongly correlated, and the distributions of REG Ialpha- and IL-22R1-positive epithelial cells were very similar. IL-22 simulation enhanced the expression of REG Ialpha protein through STAT3 tyrosine phosphorylation in colon cancer cells. The IL-22-responsive element was located between -142 and -134 in the REG Ialpha promoter region. REG Ialpha protein may have a pathophysiological role as a biological mediator for immune cell-derived IL-22 in the UC mucosa.

Biology of interleukin-22

Interleukin (IL)-22 is a member of the IL-10 family of cytokines and represents an important effector molecule of activated Th22, Th1, and Th17 cells, as well as Tc-cell subsets, gammadelta T cells, natural killer (NK), and NKT cells. IL-22 mediates its effects via a heterodimeric transmembrane receptor complex consisting of IL-22R1 and IL-10R2 and subsequent Janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling pathways including Jak1, Tyk2, and STAT3. Whereas in some aspects, IL-22 acts synergistically with tumor necrosis factor-alpha, IL-1beta, or IL-17, most functions of IL-22 are unique. Importantly, IL-22 does not serve the communication between immune cells. It mainly acts on epithelial cells and hepatocytes, where it favors the antimicrobial defense, regeneration, and protection against damage and induces acute phase reactants and some chemokines. This chapter illuminates in detail the properties of IL-22 with respect to its gene, protein structure, cellular sources, receptors, target cells, biological effects, and, finally, its role in chronic inflammatory diseases, tumors, and infection.

Th17 cytokines and the gut mucosal barrier

Local immune responses serve to contain infections by pathogens to the gut while preventing pathogen dissemination to systemic sites. Several subsets of T cells in the gut (T-helper 17 cells, gammadelta T cells, natural killer (NK), and NK-T cells) contribute to the mucosal response to pathogens by secreting a subset of cytokines including interleukin (IL)-17A, IL-17F, IL-22, and IL-26. These cytokines induce the secretion of chemokines and antimicrobial proteins, thereby orchestrating the mucosal barrier against gastrointestinal pathogens. While the mucosal barrier prevents bacterial dissemination from the gut, it also promotes colonization by pathogens that are resistant to some of the inducible antimicrobial responses. In this review, we describe the contribution of Th17 cytokines to the gut mucosal barrier during bacterial infections.

Role of nuclear unphosphorylated STAT3 in angiotensin II type 1 receptor-induced cardiac hypertrophy

AIMS

Cardiac hypertrophy is a risk factor independent of blood pressure; however, the mechanisms that distinguish pathological remodelling due to local cues from pressure overload are unresolved. This study was aimed at discovering a novel gene expression mechanism in heart failure.

METHODS AND RESULTS

In angiotensin II type 1 receptor (AT1R) transgenic mice (TG), we found a significant increase of mRNA and total STAT3 (T-STAT3) protein, but not STAT3 phosphorylated at residues Y705 and S727. A net increase in nuclear accumulation of this unphosphorylated form of STAT3 (U-STAT3) correlated with the development of cardiac hypertrophy and dysfunction, which are associated with abnormal expression of osteopontin and regulator of G protein signalling 2 genes. Nuclear accumulation of U-STAT3 is induced by angiotensin II treatment in neonatal cardiac myocytes, fibroblasts, and AT1R-expressing human embryonic kidney 293 (HEK-AT1R) cells. Chromatin immunoprecipitation demonstrated that U-STAT3 binds to the target gene promoter, and siRNA-mediated knockdown of STAT3 expression significantly altered the expression of target genes in HEK-AT1R cells. T-STAT3 in TG mouse hearts and the phosphorylation-deficient Y705F mutant STAT3 in HEK-AT1R cells physically interacted with transcription co-activator p300.

CONCLUSION

Chronic activation of AT1R induces unregulated expression of the Stat3 gene, leading to nuclear accumulation of U-STAT3, which significantly correlated with progression of cardiac hypertrophy.

Th17 cytokines and host-pathogen interactions at the mucosa: dichotomies of help and harm

The mucosal surfaces are often the first site of interaction between pathogenic microorganisms and the host. Activation of the mucosal immune response has the important function of containing an infection and preventing dissemination of pathogens to systemic sites (barrier function). Numerous lines of evidence suggest that the barrier function is orchestrated by a subset of cytokines (interleukin (IL-)17 and IL-22), which belong to the Th17 family. IL-17 and IL-22 induce expression of antimicrobial peptides and neutrophil chemoattractants at mucosal sites, and thus play an important role in controlling mucosal infections. However, there is increasing evidence that mucosal pathogens achieve greater colonization during inflammation because they are resistant to a subset of these antimicrobial responses. In this review we compare the antimicrobial responses elicited by Th17 cytokines during mucosal infections with four different pathogens: Klebsiella pneumoniae, Citrobacter rodentium, Candida albicans and Salmonella typhimurium. We will then discuss which responses may constitute the mucosal barrier, thus providing a benefit to the host, and which ones may promote the colonization of pathogens, thereby providing a benefit to the microbes.

Dexamethasone suppresses interleukin-22 associated with bacterial infection in vitro and in vivo

Interleukin (IL)-22 production triggered by innate immune mechanisms has been identified as key to efficient intestinal anti-bacterial host defence and preservation of homeostasis. We hypothesized that glucocorticoid therapy may impair IL-22 expression, which should promote intestinal epithelial damage with the potential of subsequent bacterial translocation. High-dose corticosteroid therapy in Crohn's disease has been associated with an increased rate of abscess formation and ultimately with a higher risk of developing postoperative infectious complications, including abdominal sepsis. Thus, we sought to investigate effects of the prototypic glucocorticoid dexamethasone on IL-22 production in the context of bacterial infection. Enhanced IL-22 plasma levels were detectable in rat sepsis. Moreover, heat-inactivated Staphylococcus epidermidis, used as a prototypic activator of innate immunity, induced robust production of IL-22 by human peripheral blood mononuclear cells (PBMC). Here, we report for the first time that dexamethasone mediates remarkable suppression of IL-22 as detected in S. epidermidis-activated PBMC and rat sepsis, respectively. The data presented herein suggest that insufficient IL-22 function may contribute to impaired intestinal host defence in the context of corticosteroid therapy.

Innate and adaptive interleukin-22 protects mice from inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease thought to be mediated by dysfunctional innate and/or adaptive immunity. This aberrant immune response leads to the secretion of harmful cytokines that destroy the epithelium of the gastrointestinal tract and thus cause further inflammation. Interleukin-22 (IL-22) is a T helper 17 (Th17) T cell-associated cytokine that is bifunctional in that it has both proinflammatory and protective effects on tissues depending on the inflammatory context. We show herein that IL-22 protected mice from IBD. Interestingly, not only was this protection mediated by CD4+ T cells, but IL-22-expressing natural killer (NK) cells also conferred protection. In addition, IL-22 expression was differentially regulated between NK cell subsets. Thus, both the innate and adaptive immune responses have developed protective mechanisms to counteract the damaging effects of inflammation on tissues.

Innate and adaptive interleukin-22 protects mice from inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease thought to be mediated by dysfunctional innate and/or adaptive immunity. This aberrant immune response leads to the secretion of harmful cytokines that destroy the epithelium of the gastrointestinal tract and thus cause further inflammation. Interleukin-22 (IL-22) is a T helper 17 (Th17) T cell-associated cytokine that is bifunctional in that it has both proinflammatory and protective effects on tissues depending on the inflammatory context. We show herein that IL-22 protected mice from IBD. Interestingly, not only was this protection mediated by CD4+ T cells, but IL-22-expressing natural killer (NK) cells also conferred protection. In addition, IL-22 expression was differentially regulated between NK cell subsets. Thus, both the innate and adaptive immune responses have developed protective mechanisms to counteract the damaging effects of inflammation on tissues.

Co-operative action of interleukin-10 and interferon-gamma to regulate dendritic cell functions

Interleukin-10 (IL-10) and interferon-gamma (IFN-gamma) double producer is found in a subpopulation of T regulatory type 1 (Tr1) and T helper type 1 (Th1) cells. Consequently, it is of interest how IL-10 and IFN-gamma influence the immune system. However, few studies have addressed the co-operative action of these 'immunosuppressive' and 'immunostimulatory' cytokines. Here, we examine the effect of IL-10 combined with IFN-gamma on dendritic cell (DC) functions. Murine bone marrow-derived conventional DCs were stimulated with IL-10 and/or IFN-gamma for 24 hr. Tumour necrosis factor-alpha and IL-12 p40 production by DCs treated with both IL-10 and IFN-gamma was significantly lower than that by DCs treated with IL-10 or IFN-gamma alone. Major histocompatibility complex class II expression on DCs treated with both cytokines was attenuated compared with that on DCs treated with either cytokine alone. In contrast, levels of inducible nitric oxide synthase and indoleamine 2,3-dioxygenase, which appear to suppress T-cell responses and promote tolerance, in DCs treated with both cytokines were higher than those in DCs treated with IL-10 or IFN-gamma alone. Simultaneous treatment with IL-10 and IFN-gamma significantly suppressed the ability of DCs to activate CD4+ T cells compared with treatment with either cytokine. Therefore, IL-10 and IFN-gamma co-operatively suppress the immunostimulatory functions of DCs.

Molecular mechanisms of IL-18BP regulation in DLD-1 cells: pivotal direct action of the STAT1/GAS axis on the promoter level

Interleukin (IL)-18, formerly known as interferon (IFN)-gamma-inducing factor, is a crucial mediator of host defence and inflammation. Control of IL-18 bioactivity by its endogenous antagonist IL-18 binding protein (IL-18BP) is a major objective of immunoregulation. IL-18BP is strongly up-regulated by IFN-gamma, thereby establishing a negative feedback mechanism detectable in cell culture and in vivo. Here we sought to investigate in D.L. Dexter (DLD) colon carcinoma cells molecular mechanisms of IL-18BP induction under the influence of IFN-gamma. Mutational analysis revealed that a proximal gamma-activated sequence (GAS) at the IL-18BP promoter is of pivotal importance for expression by IFN-gamma-activated cells. Use of siRNA underscored the essential role of the signal transducer and activator of transcription (STAT)-1 in this process. Indeed, electrophoretic mobility shift assay and chromatin immunoprecipitation analysis proved STAT1 binding to this particular GAS site. Maximal expression of IL-18BP was dependent on de novo protein synthesis but unaffected by silencing of interferon regulatory factor-1. Altogether, data presented herein indicate that direct action of STAT1 on the IL-18BP promoter at the proximal GAS element is key to IL-18BP expression by IFN-gamma-stimulated DLD-1 colon carcinoma cells.

Simian immunodeficiency virus-induced mucosal interleukin-17 deficiency promotes Salmonella dissemination from the gut

Salmonella typhimurium causes a localized enteric infection in immunocompetent individuals, whereas HIV-infected individuals develop a life-threatening bacteremia. Here we show that simian immunodeficiency virus (SIV) infection results in depletion of T helper type 17 (TH17) cells in the ileal mucosa of rhesus macaques, thereby impairing mucosal barrier functions to S. typhimurium dissemination. In SIV-negative macaques, the gene expression profile induced by S. typhimurium in ligated ileal loops was dominated by TH17 responses, including the expression of interleukin-17 (IL-17) and IL-22. TH17 cells were markedly depleted in SIV-infected rhesus macaques, resulting in blunted TH17 responses to S. typhimurium infection and increased bacterial dissemination. IL-17 receptor-deficient mice showed increased systemic dissemination of S. typhimurium from the gut, suggesting that IL-17 deficiency causes defects in mucosal barrier function. We conclude that SIV infection impairs the IL-17 axis, an arm of the mucosal immune response preventing systemic microbial dissemination from the gastrointestinal tract.

T cells help to amplify inflammatory responses induced by Salmonella enterica serotype Typhimurium in the intestinal mucosa

Salmonella enterica serotype Typhimurium causes an acute inflammatory reaction in the ceca of streptomycin-pretreated mice. We determined global changes in gene expression elicited by serotype Typhimurium in the cecal mucosa. The gene expression profile was dominated by T-cell-derived cytokines and genes whose expression is known to be induced by these cytokines. Markedly increased mRNA levels of genes encoding gamma interferon (IFN-gamma), interleukin-22 (IL-22), and IL-17 were detected by quantitative real-time PCR. Furthermore, the mRNA levels of genes whose expression is induced by IFN-gamma, IL-22, or IL-17, including genes encoding macrophage inflammatory protein 2 (MIP-2), inducible nitric oxide synthase (Nos2), lipocalin-2 (Lcn2), MIP-1alpha, MIP-1beta, and keratinocyte-derived cytokine (KC), were also markedly increased. To assess the importance of T cells in orchestrating this proinflammatory gene expression profile, we depleted T cells by using a monoclonal antibody prior to investigating cecal inflammation caused by serotype Typhimurium in streptomycin-pretreated mice. Depletion of CD3+ T cells resulted in a dramatic reduction in gross pathology, a significantly reduced recruitment of neutrophils, and a marked reduction in mRNA levels of Ifn-gamma, Il-22, Il-17, Nos2, Lcn2, and Kc. Our results suggest that T cells play an important role in amplifying inflammatory responses induced by serotype Typhimurium in the cecal mucosa.