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

A comparative study on the immune response in the head and trunk kidney of yellow catfish infected with Edwardsiella ictaluri

The teleost kidneys are anatomically divided into head kidney and trunk kidney, each performing distinct physiological functions. Although previous research has elucidated the role of the head kidney in immune responses, there is a paucity of literature on the comparative studies of the head and trunk kidney response to bacterial infection. Therefore, an Edwardsiella ictaluri infection model of yellow catfish was constructed to investigate and compare the immune responses between the two kidney types. The findings indicated that E. ictaluri infection induced significant pathological changes in both the head and trunk kidney. Despite variances in structure, both the head and trunk kidney of yellow catfish exhibit robust immune responses following E. ictaluri infection. Unexpectedly, the up-regulation level of IgM was found to be higher in the trunk kidney compared to the head kidney. Additionally, both the IgM+ and IgD+ B cells were increased after bacterial infection. This research elucidates the parallels and distinctions in immune functions between both the head and trunk kidney in fish, enriching the immune theory of the fish kidney, and also providing a theoretical basis for the immune response of teleost kidney against bacterial infections.

Identification and multimodal characterization of a specialized epithelial cell type associated with Crohn's disease

Crohn's disease (CD) is a complex chronic inflammatory disorder with both gastrointestinal and extra-intestinal manifestations associated immune dysregulation. Analyzing 202,359 cells from 170 specimens across 83 patients, we identify a distinct epithelial cell type in both terminal ileum and ascending colon (hereon as 'LND') with high expression of LCN2, NOS2, and DUOX2 and genes related to antimicrobial response and immunoregulation. LND cells, confirmed by in-situ RNA and protein imaging, are rare in non-IBD controls but expand in active CD, and actively interact with immune cells and specifically express IBD/CD susceptibility genes, suggesting a possible function in CD immunopathogenesis. Furthermore, we discover early and late LND subpopulations with different origins and developmental potential. A higher ratio of late-to-early LND cells correlates with better response to anti-TNF treatment. Our findings thus suggest a potential pathogenic role for LND cells in both Crohn's ileitis and colitis.

Zebrafish nos2a benefits bacterial proliferation via suppressing ROS and inducing NO production to impair the expressions of inflammatory cytokines and antibacterial genes

The enzyme nitric oxide synthase 2 or inducible NOS (NOS2), reactive oxygen species (ROS) and nitric oxide (NO) are important participants in various inflammatory and immune responses. However, the functional significances of the correlations among piscine NOS2, ROS and NO during pathogen infection remain unclear. In teleost, there are two nos2 genes (nos2a and nos2b). It has been previously reported that zebrafish nos2a behaves as a classical inducible NOS, and nos2b exerts some functions similar to mammalian NOS3. In the present study, we reported the functional characterization of zebrafish nos2a during bacterial infection. We found that zebrafish nos2a promoted bacterial proliferation, accompanied by an increased susceptibility to Edwardsiella piscicida infection. The nagative regulation of zebrafish nos2a during E. piscicida infection was characterized by the impaired ROS levels, the induced NO production and the decreased expressions of proinflammatory cytokines, antibacterial genes and oxidant factors. Furthermore, although both inducing ROS and inhibiting NO production significantly inhibited bacterial proliferation, only inhibiting NO production but not inducing ROS significantly increased resistance to E. piscicida infection. More importantly, ROS supplementation and inhibition of NO completely abolished this detrimental consequence mediated by zebrafish nos2a during E. piscicida infection. All together, these results firstly demonstrate that the innate response mediated by zebrafish nos2a in promoting bacterial proliferation is dependent on the lower ROS level and higher NO production. The present study also reveals that inhibition of NO can be effective in the protection against E. piscicida infection.

A Specialized Epithelial Cell Type Regulating Mucosal Immunity and Driving Human Crohn's Disease

Crohn's disease (CD) is a complex chronic inflammatory disorder that may affect any part of gastrointestinal tract with extra-intestinal manifestations and associated immune dysregulation. To characterize heterogeneity in CD, we profiled single-cell transcriptomics of 170 samples from 65 CD patients and 18 non-inflammatory bowel disease (IBD) controls in both the terminal ileum (TI) and ascending colon (AC). Analysis of 202,359 cells identified a novel epithelial cell type in both TI and AC, featuring high expression of LCN2, NOS2, and DUOX2, and thus is named LND. LND cells, confirmed by high-resolution in-situ RNA imaging, were rarely found in non-IBD controls, but expanded significantly in active CD. Compared to other epithelial cells, genes defining LND cells were enriched in antimicrobial response and immunoregulation. Moreover, multiplexed protein imaging demonstrated that LND cell abundance was associated with immune infiltration. Cross-talk between LND and immune cells was explored by ligand-receptor interactions and further evidenced by their spatial colocalization. LND cells showed significant enrichment of expression specificity of IBD/CD susceptibility genes, revealing its role in immunopathogenesis of CD. Investigating lineage relationships of epithelial cells detected two LND cell subpopulations with different origins and developmental potential, early and late LND. The ratio of the late to early LND cells was related to anti-TNF response. These findings emphasize the pathogenic role of the specialized LND cell type in both Crohn's ileitis and Crohn's colitis and identify novel biomarkers associated with disease activity and treatment response.

[Molecular diagnosis of hand eczema]

BACKGROUND

Because hand eczema is a diagnostic challenge even for experienced dermatologists, a correct diagnosis is essential to ensure success of specific therapies.

OBJECTIVES

Prerequisites for successful molecular diagnostics in general and in hand eczema in particular are discussed.

MATERIALS AND METHODS

Basic research and opinion statement on new developments in molecular diagnostics are considered with a special focus on hand eczema.

RESULTS

The first molecular classifier to distinguish psoriasis from (hand) eczema signature has been introduced as CE-marked in vitro diagnostics (CE-IVD); many more biomarkers associated with diagnostics, theranostics, or natural course of the disease are currently being investigated.

CONCLUSIONS

Diagnosis of hand eczema will be supported by molecular diagnostics in the near future; we are at the beginning of the molecular era in dermatology.

Th17, Th22, and Myeloid-Derived Suppressor Cell Population Dynamics and Response to IL-6 in 4T1 Mammary Carcinoma

Immunotherapies relying on type 1 immunity have shown robust clinical responses in some cancers yet remain relatively ineffective in solid breast tumors. Polarization toward type 2 immunity and expansion of myeloid-derived suppressor cells (MDSC) confer resistance to therapy, though it remains unclear whether polarization toward type 3 immunity occurs or has a similar effect. Therefore, we investigated the involvement of type 3 T_h17 and T_h22 cells and their association with expanding MDSC populations in the 4T1 mouse mammary carcinoma model. T_h17 and T_h22 were detected in the earliest measurable mass at d 14 and remained present until the final sampling on d 28. In peripheral organs, T_h17 populations were significantly higher than the non-tumor bearing control and peaked early at d 7, before a palpable tumor had formed. Peripheral T_h22 proportions were also significantly increased, though at later times when tumors were established. To further address the mechanism underlying type 3 immune cell and MDSC recruitment, we used CRISPR-Cas9 to knock out 4T1 tumor production of interleukin-6 (4T1-IL-6-KO), which functions in myelopoiesis, MDSC recruitment, and T_h maturation. While 4T1-IL-6-KO tumor growth was similar to the control, the reduced IL-6 significantly expanded the total CD4⁺ T_h population and T_h17 in tumors, while T_h22 and MDSC were reduced in all tissues; this suggests that clinical IL-6 depletion combined with immunotherapy could improve outcomes. In sum, 4T1 mammary carcinomas secrete IL-6 and other factors, to polarize and reshape T_h populations and expand distinct T_h17 and T_h22 populations, which may facilitate tumor growth and confer immunotherapy resistance.

Functional characterization of arginine metabolic pathway enzymes in the antibacterial immune response of penaeid shrimp

Arginine metabolism pathway enzymes and products are important modulators of several physiological processes in animals, including immune response. Although some components of the arginine metabolic pathway have been reported in penaeid shrimps, no systematic study has explored all the key pathway enzymes involved in shrimp antimicrobial response. Here, we explored the role of the three key arginine metabolism enzymes (nitric-oxide synthase (NOS), arginase (ARG), agmatinase (AGM)) in Penaeus vannamei antimicrobial immunity. First, P. vannamei homologs of ARG and AGM (PvARG and PvAGM) were cloned and found to be evolutionally conserved with invertebrate counterparts. Transcript levels of PvARG, PvAGM, and PvNOS were ubiquitously expressed in healthy shrimp tissues and induced in hemocytes and hepatopancreas upon challenge with Gram-negative (Vibrio parahaemolyticus) and Gram-positive (Streptoccocus iniae) bacteria, suggesting their involvement in shrimp antimicrobial immune response. Besides, RNA interference knockdown and enzyme activity assay revealed an antagonistic relationship between PvARG/PvAGM and PvNOS, while this relationship was broken upon pathogen stimulation. Interestingly, knockdown of PvNOS increased Vibrio abundance in shrimp hemolymph, whereas knockdown of PvAGR reduced Vibrio abundance. Taken together, our present data shows that homologs of the key arginine metabolism pathway enzymes in penaeid shrimp (PvARG, PvAGM, and PvNOS) work synergistically and/or antagonistically to modulate antibacterial immune response.

Neutralization of IL-17 and treatment with IL-2 protects septic arthritis by regulating free radical production and antioxidant enzymes in Th17 and Tregs: An immunomodulatory TLR2 versus TNFR response

Septic arthritis is a destructive joint disease caused by Staphylococcus aureus. Synovial inflammation involved Th17 proliferation and down regulation of Treg population, thus resolution of inflammation targeting IL-17 may be important to control arthritis. Endogenous inhibition of IL-17 to regulate arthritic inflammation correlating with Th17/Treg cells TLR2 and TNFRs are not done. The role of SOD, CAT and GRx in relation to ROS production during arthritis along with expression of TLR2, TNFR1/TNFR2 in Th17/Treg cells of mice treated with IL-17A Ab/ IL-2 were studied. Increased ROS, reduced antioxidant enzyme activity was found in Th17 cells of SA infected mice whereas Treg cells of IL-17A Ab/ IL-2 treated group showed opposite effects. Neutralization of IL-17 after arthritis cause decreased TNFR1 and increased TNFR2 expression in Treg cells. Thus, neutralization of IL-17 or IL-2 treatment regulates septic arthritis by enhancing anti-inflammatory properties of Treg via antioxidant balance and modulating TLR2/TNFR response.

Acetaminophen-Induced Liver Injury Exposes Murine IL-22 as Sex-Related Gene Product

Gaining detailed knowledge about sex-related immunoregulation remains a crucial prerequisite for the development of adequate disease models and therapeutic strategies enabling personalized medicine. Here, the key parameter of the production of cytokines mediating disease resolution was investigated. Among these cytokines, STAT3-activating interleukin (IL)-22 is principally associated with recovery from tissue injury. By investigating paradigmatic acetaminophen-induced liver injury, we demonstrated that IL-22 expression is enhanced in female mice. Increased female IL-22 was confirmed at a cellular level using murine splenocytes stimulated by lipopolysaccharide or αCD3/CD28 to model innate or adaptive immunoactivation. Interestingly, testosterone or dihydrotestosterone reduced IL-22 production by female but not by male splenocytes. Mechanistic studies on PMA/PHA-stimulated T-cell-lymphoma EL-4 cells verified the capability of testosterone/dihydrotestosterone to reduce IL-22 production. Moreover, we demonstrated by chromatin immunoprecipitation that testosterone impairs binding of the aryl hydrocarbon receptor to xenobiotic responsive elements within the murine IL-22 promoter. Overall, female mice undergoing acute liver injury and cultured female splenocytes upon inflammatory activation display increased IL-22. This observation is likely related to the immunosuppressive effects of androgens in males. The data presented concur with more pronounced immunological alertness demonstrable in females, which may relate to the sex-specific course of some immunological disorders.

Comparative evaluation of the protective effects of oral administration of auraptene and umbelliprenin against CFA-induced chronic inflammation with polyarthritis in rats

This study aimed to evaluate the anti-inflammatory effect of Auraptene (AUR) and Umbelliprenin (UMB) in a rat model of rheumatoid arthritis (RA) induced by using complete Freund's adjuvant (CFA). Paw swelling of adjuvant arthritis rats measured at various times after CFA injection. Over 15 days of RA induction, mediator/cytokine-mediated processes involved in managing the regulation and resolving RA's inflammation were also quantified with ELISA. Histopathological changes were also assessed under a microscope 15 days after the CFA injection. AUR at all doses and UMB administration only at a 16 mM /kg administration dose significantly reduced CFA-induced paw edema level compared to the control group. UMB (64 and 32 mM) and AUR (64, 32, and 16 mM) could reduce the PGE2 (p < .0001-.01) and NO (p < .0001-.05) levels in the treatment groups compared to the negative control group. However, these compounds showed no significant effect on the TNF-α, IFN-γ, TGF-β, IL-4, and IL-10 levels than the control group (p > .05). Unlike indomethacin and prednisolone, treatment of rats with AUR (16, 32, and 64 mM/kg) and UMB (16 and 32 mM/kg) reduced the level of IL-2 (p < .0001). In all treatment groups, the serum level of IL-17 was significantly reduced compared to the CFA group (p < .001-0.05). We suggested AUR and UMB could diminish inflammation by reducing the serum level of IL-17 and could be considered a proper alternative in the treatment of IL-17 related inflammatory diseases such as rheumatoid arthritis. Given that AUR and UMB apply their anti-inflammatory effects by changing distinct cytokine release/inhibition patterns, their potential application in diverse inflammatory diseases seems different.

Host immune response against leishmaniasis and parasite persistence strategies: A review and assessment of recent research

Leishmaniasis, a neglected parasitic disease caused by a unicellular protozoan of the genus Leishmania, is transmitted through the bite of a female sandfly. The disease remains a major public health problem and is linked to tropical and subtropical regions, with an endemic picture in several regions, including East Africa, the Mediterranean basin and South America. The different causative species display a diversity of clinical presentations; therefore, the immunological data on leishmaniasis are both scarce and controversial for the different forms and infecting species of the parasite. The present review highlights the main immune parameters associated with leishmaniasis that might contribute to a better understanding of the pathogenicity of the parasite and the clinical outcomes of the disease. Our aim was to provide a concise overview of the immunobiology of the disease and the factors that influence it, as this knowledge may be helpful in developing novel chemotherapeutic and vaccine strategies.

Inhibitory effect of particulate matter on toll-like receptor 9 stimulated dendritic cells by downregulating mitogen-activated protein kinase and NF-κB pathway

Ambient particulate matter (PM) is associated with adverse health consequences. However, the influence of PM on the innate immune system is poorly understood. The aim of the present study was to examine the effect of diesel particulate matter 2.5 μm (PM_2.5, SRM1650b) on dendritic cells. PM_2.5 significantly reduced cytokine levels of interleukin (IL)-12 p40, IL-6 and TNF-α levels in CpG-DNA (TLR9 ligand)-stimulated dendritic cells. To determine the mechanisms underlying this observed inhibition induced by PM_2.5, western blot analysis was conducted. PM_2.5 was found to downregulate ERK1/2, JNK1/2, p38 MAPKs, and NF-κB pathways. PM_2.5 exposure decreased TLR9-dependent NF-κB and activator protein (AP-1) reporter luciferase activities. Our findings demonstrate that PM_2.5 reduced the production of cytokines which may be associated with inhibition of MAPK and NF-κB signaling pathway. Further, data suggest the immunosuppressive effect of PM_2.5 on the innate immune cells may lead to serious damage to the host immune system.

The microbiota programs DNA methylation to control intestinal homeostasis and inflammation

Although much research has been done on the diversity of the gut microbiome, little is known about how it influences intestinal homeostasis under normal and pathogenic conditions. Epigenetic mechanisms have recently been suggested to operate at the interface between the microbiota and the intestinal epithelium. We performed whole-genome bisulfite sequencing on conventionally raised and germ-free mice, and discovered that exposure to commensal microbiota induced localized DNA methylation changes at regulatory elements, which are TET2/3-dependent. This culminated in the activation of a set of 'early sentinel' response genes to maintain intestinal homeostasis. Furthermore, we demonstrated that exposure to the microbiota in dextran sodium sulfate-induced acute inflammation results in profound DNA methylation and chromatin accessibility changes at regulatory elements, leading to alterations in gene expression programs enriched in colitis- and colon-cancer-associated functions. Finally, by employing genetic interventions, we show that microbiota-induced epigenetic programming is necessary for proper intestinal homeostasis in vivo.

Role of Th17 and Treg cells in septic arthritis and the impact of the Th17/Treg -derived cytokines in the pathogenesis of S. aureus induced septic arthritis in mice

Intravenous inoculation of Swiss mice with S. aureus leads to severe synovial joint tissue swelling along with prominent T lymphocyte infiltrate with associated inflammation in synovial tissue. Cytokines released from macrophages such as TNF-α, IL-1β and IL-6 the main players that precede cartilage and bone destruction during septic arthritis (SA) followed by osteoclast differentiation and bone resorption. CD4⁺ naïve T cells upon cytokine driven activation, differentiate into lineages of helper (Th) and regulatory T cells (Treg) including inflammatory Th17 cell lineage. Acting as counterbalance, Tregs protect the host by releasing anti-inflammatory IL-10. A disturbed balance between Th17 and Treg cell development skews the pathways towards Th17 lineage, but how it actually induces SA is still unexplored. Therefore, this study has been attempted to demonstrate the Th17/Treg ratio in synovial tissue, spleen and peripheral blood by FACS and their derived cytokines from serum of arthritic mice. Here, we reported that the ratios of Th17/Treg as well as their related cytokine levels were increased at 3 days post-infection which was decreased during 9 DPI but heightened again at 15DPI resulting in persistence of the disease, though decreased again at 30 DPI even in animals with increased dose of infection. Bacterial colonies were present in synovial joints at 15 DPI in animals with increased infection but found to be absent at 30 DPI. Maintaining Th17/Treg balance by neutralizing functionally active Th17 and their related cytokines or adoptive transfer of fully active Tregs and/or their related cytokines may lead to a novel therapeutic strategy for combating Staphylococcal arthritis.

Type I Interferon Supports Inducible Nitric Oxide Synthase in Murine Hepatoma Cells and Hepatocytes and during Experimental Acetaminophen-Induced Liver Damage

Cytokine regulation of high-output nitric oxide (NO) derived from inducible NO synthase (iNOS) is critically involved in inflammation biology and host defense. Herein, we set out to characterize the role of type I interferon (IFN) as potential regulator of hepatic iNOS in vitro and in vivo. In this regard, we identified in murine Hepa1-6 hepatoma cells a potent synergism between pro-inflammatory interleukin-β/tumor necrosis factor-α and immunoregulatory IFNβ as detected by analysis of iNOS expression and nitrite release. Upregulation of iNOS by IFNβ coincided with enhanced binding of signal transducer and activator of transcription-1 to a regulatory region at the murine iNOS promoter known to support target gene expression in response to this signaling pathway. Synergistic iNOS induction under the influence of IFNβ was confirmed in alternate murine Hepa56.1D hepatoma cells and primary hepatocytes. To assess iNOS regulation by type I IFN in vivo, murine acetaminophen (APAP)-induced sterile liver inflammation was investigated. In this model of acute liver injury, excessive necroinflammation drives iNOS expression in diverse liver cell types, among others hepatocytes. Herein, we demonstrate impaired iNOS expression in type I IFN receptor-deficient mice which associated with diminished APAP-induced liver damage. Data presented indicate a vital role of type I IFN within the inflamed liver for fine-tuning pathological processes such as overt iNOS expression.

Response of iNOS and its relationship with IL-22 and STAT3 in macrophage activity in the polar forms of leprosy

Leprosy is a chronic granulomatous infection that manifests as different clinical forms related to the immunological response. The aim of the study was to evaluated the response of IL-22, STAT3, CD68 and iNOS in leprosy skin lesions. The mean number IL-22 positive cells was 12.12±1.90cells/field in the TT form and 31.31±2.91cells/field in the LL form. STAT3 positive cells was 5.29±1.96 cells/field in the TT form, while this number was 11.13±3.48cells/field in the LL form. The mean number of CD68 positive cells was 25.18±6.21cells/field in the TT form and 62.81±8.13cells/field in the LL form. Quantitative analysis of iNOS revealed a significant difference, with the mean number of cells expressing the enzyme being 30.24±2.88cells/field in the TT form compared to 35.44±4.69cells/field in the LL form. Linear correlations in lesions of TT patients showed a moderate positive correlations between CD68 and iNOS, STAT3 and Inos, IL-22 and STAT3, and IL-22 and iNOS. Our results demonstrate that these factors can act synergistically to induce a microbicidal activity in the population of macrophages in the leprosy lesions.

Sex Bias in Pathogenesis of Autoimmune Neuroinflammation: Relevance for Dimethyl Fumarate Immunomodulatory/Anti-oxidant Action

In the present study, upon showing sexual dimorphism in dimethyl fumarate (DMF) efficacy to moderate the clinical severity of experimental autoimmune encephalomyelitis (EAE) in Dark Agouti rats, cellular and molecular substrate of this dimorphism was explored. In rats of both sexes, DMF administration from the day of immunization attenuated EAE severity, but this effect was more prominent in males leading to loss of the sexual dimorphism observed in vehicle-administered controls. Consistently, in male rats, DMF was more efficient in diminishing the number of CD4+ T lymphocytes infiltrating spinal cord (SC) and their reactivation, the number of IL-17+ T lymphocytes and particularly cellularity of their highly pathogenic IFN-γ+GM-CSF+IL-17+ subset. This was linked with changes in SC CD11b+CD45+TCRαβ- microglia/proinflammatory monocyte progeny, substantiated in a more prominent increase in the frequency of anti-inflammatory phygocyting CD163+ cells and the cells expressing high surface levels of immunoregulatory CD83 molecule (associated with apoptotic cells phagocytosis and implicated in downregulation of CD4+ T lymphocyte reactivation) among CD11b+CD45+TCRαβ- cells in male rat SC. These changes were associated with greater increase in the nuclear factor (erythroid-derived 2)-like 2 expression in male rats administered with DMF. In accordance with the previous findings, DMF diminished reactive nitrogen and oxygen species generation and consistently, SC level of advanced oxidation protein products, to the greater extent in male rats. Overall, our study indicates sex-specificity in the sensitivity of DMF cellular and molecular targets and encourages sex-based clinical research to define significance of sex for action of therapeutic agents moderating autoimmune neuroinflammation-/oxidative stress-related nervous tissue damage.

Melatonin Pharmacological Blood Levels Increase Total Antioxidant Capacity in Critically Ill Patients

In this study, the aim was to test the biochemical effects of melatonin supplementation in Intensive Care Unit (ICU) patients, since their blood levels are decreased. Sixty-four patients were enrolled in the study. From the evening of the 3rd ICU day, patients were randomized to receive oral melatonin (3 mg, group M) or placebo (group P) twice daily, at 20:00 and 24:00, until discharged. Blood was taken (at 00:00 and 14:00), on the 3rd ICU day to assess basal nocturnal melatonin values, and then during the treatment period on the 4th and 8th ICU days. Melatonin, total antioxidant capacity, and oxidative stress were evaluated in serum. Melatonin circadian rhythm before treatment was similar in the two groups, with a partial preservation of the cycle. Four hours from the 1st administration (4th ICU day, 00:00), melatonin levels increased to 2514 (982.3; 7148) pg·mL⁻¹ in group M vs. 20.3 (14.7; 62.3) pg·mL⁻¹ in group P (p < 0.001). After five treatment days (8th ICU day), melatonin absorption showed a repetitive trend in group M, while in group P nocturnal secretion (00:00) was impaired: 20 (11.5; 34.5) pg·mL⁻¹ vs. 33.8 (25.0; 62.2) on the 3rd day (p = 0.029). Immediately from the beginning of treatment, the total antioxidant capacity was significantly higher in melatonin treated subjects at 00:00; a significant correlation was found between total antioxidant capacity and blood melatonin values (ρ = 0.328; p < 0.001). The proposed enteral administration protocol was adequate, even in the early phase, to enhance melatonin blood levels and to protect the patients from oxidative stress. The antioxidant effect of melatonin could play a meaningful role in the care and well-being of these patients.

The potential role of Osteopontin in the maintenance of commensal bacteria homeostasis in the intestine

Osteopontin (Opn), a multifunctional extracellular matrix protein, is implicated in the pathogenesis of various inflammatory disorders. Under physiologic conditions, its expression is restricted to certain tissues including bone and kidney tubule. However, cellular activation during disease development induces Opn expression in various immune cells. In this study, using Opn-EGFP knock-in (KI) mice we found that CD8α⁺ T cells in the intestinal tissues, including Peyer’s patch, lamina propria and epithelium, express Opn under steady state conditions. Therefore, we examined the role of Opn-expressing CD8α⁺ T cells in intestinal homeostasis. Interestingly, Opn knockout (KO) mice had altered fecal microflora concordant with a reduction of TCRγδ⁺ intraepithelial lymphocytes (IELs). Consistent with this result, both treatment with anti-Opn blocking antibody and deficiency of Opn resulted in decreased survival of TCRγδ⁺ and TCRαβ⁺ IELs. This data suggests that a possibility that Opn may function as a survival factor for IELs in the intestinal tissue. Collectively, these data suggest the possibility that Opn might regulate the homeostasis of intestinal microflora through maintenance of TCRγδ⁺ IELs, possibly by support of IEL survival.

Toll-Like Receptor 2 Is Required for Inflammatory Process Development during Leishmania infantum Infection

Visceral leishmaniasis (VL) is a chronic and fatal disease caused by Leishmania infantum in Brazil. Leukocyte recruitment to infected tissue is a crucial event for the control of infections such as VL. Among inflammatory cells, neutrophils are recruited to the site of Leishmania infection, and these cells may control parasite replication through oxidative or non-oxidative mechanisms. The recruitment, activation and functions of the neutrophils are coordinated by pro-inflammatory cytokines and chemokines during recognition of the parasite by pattern recognition receptors (PRRs). Here, we demonstrated that the Toll-like receptor 2 (TLR2) signaling pathway contributes to the development of the innate immune response during L. infantum infection. The protective mechanism is related to the appropriate recruitment of neutrophils to the inflammatory site. Neutrophil migration is coordinated by DCs that produce CXCL1 and provide a prototypal Th1 and Th17 environment when activated via TLR2. Furthermore, infected TLR2^−/− mice failed to induce nitric oxide synthase (iNOS) expression in neutrophils but not in macrophages. In vitro, infected TLR2^−/− neutrophils presented deficient iNOS expression, nitric oxide (NO) and TNF-α production, decreased expression of CD11b and reduced L. infantum uptake capacity. The non-responsive state of neutrophils is associated with increased amounts of IL-10. Taken together, these data clarify new mechanisms by which TLR2 functions in promoting the development of the adaptive immune response and effector mechanisms of neutrophils during L. infantum infection.

An In Vitro Co-culture Mouse Model Demonstrates Efficient Vaccine-Mediated Control of Francisella tularensis SCHU S4 and Identifies Nitric Oxide as a Predictor of Efficacy

Francisella tularensis is a highly virulent intracellular bacterium and cell-mediated immunity is critical for protection, but mechanisms of protection against highly virulent variants, such as the prototypic strain F. tularensis strain SCHU S4, are poorly understood. To this end, we established a co-culture system, based on splenocytes from naïve, or immunized mice and in vitro infected bone marrow-derived macrophages that allowed assessment of mechanisms controlling infection with F. tularensis. We utilized the system to understand why the clpB gene deletion mutant, ΔclpB, of SCHU S4 shows superior efficacy as a vaccine in the mouse model as compared to the existing human vaccine, the live vaccine strain (LVS). Compared to naïve splenocytes, ΔclpB-, or LVS-immune splenocytes conferred very significant control of a SCHU S4 infection and the ΔclpB-immune splenocytes were superior to the LVS-immune splenocytes. Cultures with the ΔclpB-immune splenocytes also contained higher levels of IFN-γ, IL-17, and GM-CSF and nitric oxide, and T cells expressing combinations of IFN-γ, TNF-α, and IL-17, than did cultures with LVS-immune splenocytes. There was strong inverse correlation between bacterial replication and levels of nitrite, an end product of nitric oxide, and essentially no control was observed when BMDM from iNOS^-/- mice were infected. Collectively, the co-culture model identified a critical role of nitric oxide for protection against a highly virulent strain of F. tularensis.

STAT3, a Key Parameter of Cytokine-Driven Tissue Protection during Sterile Inflammation - the Case of Experimental Acetaminophen (Paracetamol)-Induced Liver Damage

Acetaminophen (APAP, N-acetyl-p-aminophenol, or paracetamol) overdosing is a prevalent cause of acute liver injury. While clinical disease is initiated by overt parenchymal hepatocyte necrosis in response to the analgetic, course of intoxication is substantially influenced by associated activation of innate immunity. This process is supposed to be set in motion by release of danger-associated molecular patterns (DAMPs) from dying hepatocytes and is accompanied by an inflammatory cytokine response. Murine models of APAP-induced liver injury emphasize the complex role that DAMPs and cytokines play in promoting either hepatic pathogenesis or resolution and recovery from intoxication. Whereas the function of key inflammatory cytokines is controversially discussed, a subclass of specific cytokines capable of efficiently activating the hepatocyte signal transducer and activator of transcription (STAT)-3 pathway stands out as being consistently protective in murine models of APAP intoxication. Those include foremost interleukin (IL)-6, IL-11, IL-13, and IL-22. Above all, activation of STAT3 under the influence of these cytokines has the capability to drive hepatocyte compensatory proliferation, a key principle of the regenerating liver. Herein, the role of these specific cytokines during experimental APAP-induced liver injury is highlighted and discussed in a broader perspective. In hard-to-treat or at-risk patients, standard therapy may fail and APAP intoxication can proceed toward a fatal condition. Focused administration of recombinant STAT3-activating cytokines may evolve as novel therapeutic approach under those ill-fated conditions.

Vascular mTOR-dependent mechanisms linking the control of aging to Alzheimer's disease

Aging is the strongest known risk factor for Alzheimer's disease (AD). With the discovery of the mechanistic target of rapamycin (mTOR) as a critical pathway controlling the rate of aging in mice, molecules at the interface between the regulation of aging and the mechanisms of specific age-associated diseases can be identified. We will review emerging evidence that mTOR-dependent brain vascular dysfunction, a universal feature of aging, may be one of the mechanisms linking the regulation of the rate of aging to the pathogenesis of Alzheimer's disease. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Correlation between nerve growth factor and tissue expression of IL-17 in leprosy

Leprosy is a serious public health problem in peripheral and developing countries. Leprosy is a chronic infectious-contagious disease caused by the intracellular, bacillus Mycobacterium leprae, which causes tissue damage and demyelination of peripheral nerves. Recent studies have demonstrated the participation of new subtype's cytokines profile in the inflammatory response of leprosy. Since nerve functions are affected by inflammatory response during the course of leprosy, changes in the production of NGF and its receptor (NGF R) may be directly associated with disability and sensory loss. Skin biopsies were collected and submitted to immunohistochemistry using specific antibodies to IL-17, NGF and NGF R. Quantitative analysis of NGF, NGFR and IL-17 immunostaining showed a significant difference between the clinical forms, with higher expression of NGF and NGFR in lepromatous leprosy and IL-17 in tuberculoid leprosy. The present study showed that IL-17, in addition to stimulating an inflammatory response, negatively regulates the action of NGF and NGF R in the polar forms of the disease.

Update on the role of Interleukin 17 in rheumatologic autoimmune diseases

Interleukin 17 is a proinflammatory cytokine produced by CD4+ T cells when in the presence of a distinct set of cytokines and other cells. Preclinical and clinical studies have assigned a role to IL-17 in tissue inflammation and damage in patients with rheumatoid arthritis, psoriasis and psoriatic arthritis, ankylosing spondylitis and systemic lupus erythematosus. Antibodies blocking the action of IL-17 have already been approved to treat patients with psoriasis and it is expected that they may also benefit patients with other rheumatic diseases.

Bordetella pertussis Adenylate Cyclase Toxin Blocks Induction of Bactericidal Nitric Oxide in Macrophages through cAMP-Dependent Activation of the SHP-1 Phosphatase

The adenylate cyclase toxin-hemolysin (CyaA) plays a key role in the virulence of Bordetella pertussis. CyaA penetrates complement receptor 3-expressing phagocytes and catalyzes uncontrolled conversion of cytosolic ATP to the key second messenger molecule cAMP. This paralyzes the capacity of neutrophils and macrophages to kill bacteria by complement-dependent oxidative burst and opsonophagocytic mechanisms. We show that cAMP signaling through the protein kinase A (PKA) pathway activates Src homology domain 2 containing protein tyrosine phosphatase (SHP) 1 and suppresses production of bactericidal NO in macrophage cells. Selective activation of PKA by the cell-permeable analog N(6)-benzoyladenosine-3',5'-cyclic monophosphate interfered with LPS-induced inducible NO synthase (iNOS) expression in RAW264.7 macrophages, whereas inhibition of PKA by H-89 largely restored the production of iNOS in CyaA-treated murine macrophages. CyaA/cAMP signaling induced SHP phosphatase-dependent dephosphorylation of the c-Fos subunit of the transcription factor AP-1 and thereby inhibited TLR4-triggered induction of iNOS gene expression. Selective small interfering RNA knockdown of SHP-1, but not of the SHP-2 phosphatase, rescued production of TLR-inducible NO in toxin-treated cells. Finally, inhibition of SHP phosphatase activity by NSC87877 abrogated B. pertussis survival inside murine macrophages. These results reveal that an as yet unknown cAMP-activated signaling pathway controls SHP-1 phosphatase activity and may regulate numerous receptor signaling pathways in leukocytes. Hijacking of SHP-1 by CyaA action then enables B. pertussis to evade NO-mediated killing in sentinel cells of innate immunity.

Inflammation characteristics in bladder pain syndrome ESSIC type 3C/classic interstitial cystitis

OBJECTIVES

Interstitial cystitis is regarded as a heterogenous syndrome with two distinguishable forms: the non-ulcer and the classic form of interstitial cystitis, the latter with Hunner's lesions; or bladder pain syndrome type 3C and non-Hunner bladder pain syndrome, respectively.

METHODS

A cohort of 379 patients diagnosed with interstitial cystitis was studied. Nitric oxide release from the bladder was measured using a chemiluminescence nitric oxide analyzer. Bladder biopsies from the patients and healthy controls were analyzed by routine histopathological examination. Biopsies from a subset of patients and controls were also analyzed by immunohistochemistry and cytokine gene expression by real-time polymerase chain reaction.

RESULTS

Patients with bladder pain syndrome type 3C/classic interstitial cystitis had considerably higher levels of nitric oxide as compared with non-Hunner bladder pain syndrome/non-ulcer interstitial cystitis patients and healthy individuals, and showed histologically a chronic inflammation in the bladder mucosa, with abundant mast cell infiltration in all layers of the bladder wall. No inflammation was noted in non-Hunner bladder pain syndrome/non-ulcer interstitial cystitis patients. The isoenzymes inducible nitric oxide synthase, the catalyst in the nitric oxide production, was strongly expressed in the inflammatory cells in the bladder mucosa of bladder pain syndrome type 3C/classic interstitial cystitis patients. In addition, the expression of the pro-inflammatory cytokines interleukin-6 and interleukin-17A messenger ribonucleic acid, and of anti-inflammatory interleukin-10 messenger ribonucleic acid showed significantly increased levels in bladder pain syndrome type 3C/classic interstitial cystitis compared with healthy controls.

CONCLUSION

Bladder pain syndrome type 3C/classic interstitial cystitis is a distinct inflammatory disease and in many aspects shares features of inflammatory autoimmune diseases. These findings could open up novel research avenues with expectations for new targets for pharmacological treatment.

Intraindividual genome expression analysis reveals a specific molecular signature of psoriasis and eczema

Previous attempts to gain insight into the pathogenesis of psoriasis and eczema by comparing their molecular signatures were hampered by the high interindividual variability of those complex diseases. In patients affected by both psoriasis and nonatopic or atopic eczema simultaneously (n = 24), an intraindividual comparison of the molecular signatures of psoriasis and eczema identified genes and signaling pathways regulated in common and exclusive for each disease across all patients. Psoriasis-specific genes were important regulators of glucose and lipid metabolism, epidermal differentiation, as well as immune mediators of T helper 17 (TH17) responses, interleukin-10 (IL-10) family cytokines, and IL-36. Genes in eczema related to epidermal barrier, reduced innate immunity, increased IL-6, and a TH2 signature. Within eczema subtypes, a mutually exclusive regulation of epidermal differentiation genes was observed. Furthermore, only contact eczema was driven by inflammasome activation, apoptosis, and cellular adhesion. On the basis of this comprehensive picture of the pathogenesis of psoriasis and eczema, a disease classifier consisting of NOS2 and CCL27 was created. In an independent cohort of eczema (n = 28) and psoriasis patients (n = 25), respectively, this classifier diagnosed all patients correctly and also identified initially misdiagnosed or clinically undifferentiated patients.

Unmasking the pathogenic role of IL-17 axis in primary Sjögren's syndrome: a new era for therapeutic targeting?

Compelling evidence suggests that the IL-17 axis plays a pivotal role in the pathogenesis of several autoimmune disorders including primary Sjögren's syndrome (pSS). However, although several studies have been carried out in experimental models and patients with pSS, many aspects of this field are not fully elucidated. In particular, the role played by different Th17 cell subsets as well as the effects of pharmacological therapies on IL-17 balance represent an intriguing issue. Furthermore, the understanding of IL-17 axis pathogenic role in pSS may be of interest for therapeutic purposes as a variety of compounds targeting IL-17, IL-17 receptor and other related cytokines and transcription factors involved in Th17 cell commitment are under intense investigation. The aim of this review article is to provide an overview of current knowledge in IL-17/Th17 cells in pSS and discuss their potential therapeutic targeting in this disease.

IL-17A induces hypo-contraction of intestinal smooth muscle via induction of iNOS in muscularis macrophages

Intestinal inflammation causes disorder in bowel motility. Th17 cytokines are involved in intestinal inflammation. To understand the role of interleukin (IL)-17 in intestinal motility, we examined effects of IL-17A on contractile activities of organ-cultured ileum. Rat ileal smooth muscle strips were organ cultured with IL-17A. Muscle contraction was measured, and cells expressing inducible nitric oxide synthase (iNOS) were identified with immunohistochemistry. Creating Th17-transferred colitis model mice, in vivo effects of IL-17 on contractile activities, and iNOS mRNA expression in colonic smooth muscle were investigated. Treatment with IL-17A for 12 h and 3 days attenuated carbachol- and membrane depolarization-induced contractions in organ-cultured rat ileum. N(G)-Nitro-l-arginine methyl ester (100 μM), a nitric oxide synthase inhibitor, completely reversed the IL-17A-induced inhibition of contractile force. Ileal tissue cultured in the presence of IL-17A showed increased expression of iNOS mRNA and protein. Immunohistochemical analysis using an iNOS antibody revealed that iNOS protein was expressed on ED2-positive muscularis macrophages. The level of iNOS mRNA was also increased in inflamed colonic smooth muscle of Th17-transferred colitis model mice. In intestinal inflammation, IL-17A induces an intestinal motility disorder through iNOS expression in muscularis macrophages.

Nitric oxide regulates BAFF expression and T cell-independent antibody responses

Whereas NO is known to regulate T cell responses, its role in regulating B cell responses remains unclear. Previous studies suggested that inducible NO synthase 2 (NOS2/iNOS) is required for normal IgA Ab responses but inhibits antiviral IgG2a Ab responses. In this study we used NOS2(-/-) mice to determine the role of NO in T cell-dependent and T cell-independent (TI)-2 Ab responses. Whereas T cell-dependent Ab responses were only modestly increased in NOS2(-/-) mice, IgM and IgG3 Ab responses as well as marginal zone B cell plasma cell numbers and peritoneal B1b B cells were significantly elevated after immunization with the TI-2 Ag 4-hydroxy-3-nitrophenyl acetyl (NP)-Ficoll. The elevated TI-2 responses in NOS2(-/-) mice were accompanied by significant increases in serum levels of BAFF/BLyS and by increases in BAFF-producing Ly6C(hi) inflammatory monocytes and monocyte-derived dendritic cells (DCs), suggesting that NO normally inhibits BAFF expression. Indeed, we found that NOS2(-/-) DCs produced more BAFF than did wild-type DCs, and addition of a NO donor to NOS2(-/-) DCs reduced BAFF production. Bone marrow chimeric mice that lack NOS2 in either nonhematopoietic or hematopoietic cells had intermediate IgM and IgG3 Ab responses after NP-Ficoll immunization, suggesting that NOS2 from both hematopoietic and nonhematopoietic sources regulates TI-2 Ab responses. Similar to NOS2(-/-) mice, depletion of Ly6C(hi) inflammatory monocytes and monocyte-derived DCs enhanced NP-specific IgM and IgG3 responses to NP-Ficoll. Thus, NO produced by inflammatory monocytes and their derivative DC subsets plays an important role in regulating BAFF production and TI-2 Ab responses.

Increased IL-17A secreting CD4+ T cells, serum IL-17 levels and exhaled nitric oxide are correlated with childhood asthma severity

BACKGROUND

Measuring fractional exhaled nitric oxide (FeNO) is a simple and non-invasive method for assessing airway inflammation. IL-17 plays an important role in T cell-dependent inflammatory response that occurs in allergic asthma, it could act as a potent activator of inducible nitric oxide synthase (iNOS) to amplify FeNO levels.

OBJECTIVES

To evaluate the differences in the CD4(+) IL-17A(+) T cell counts, serum IL-17 levels, and FeNO levels in children with mild intermittent to moderate to severe persistent asthma classified by using the Global Initiative for Asthma (GINA).

METHODS

One hundred and twenty asthmatic children divided into the mild intermittent (n = 42), mild persistent (n = 42), and moderate to severe persistent (n = 36) groups, and 20 healthy controls were recruited for the study. Information obtained at visits included the assessment of asthma severity according to GINA guidelines and C-ACT, lung function parameters, FeNO levels, CD4(+) IL-17A(+) T cells counts from PBMCs, iNOS production by sputum cells and serum IL-17 levels.

RESULTS

Serum IL-17 and FeNO levels were significantly higher in mild to severe persistent asthmatic patients than in intermittent asthmatics or healthy controls (P < 0.05). The percentage of CD4(+) IL-17A(+) T cells was higher in moderate to severe persistent asthmatics than in mild asthmatics (P < 0.01). Moderate to severe asthmatics (n = 5) exhibited greater iNOS production in sputum cells than mild cases (n = 5). Decreased iNOS expression in sputum cells was noted in all subjects after IL-17 neutralizing antibody (P < 0.05). Serum IL-17 levels were positively correlated with FeNO (rho = 0.74; P < 0.01), negatively correlated with C-ACT (rho = -0.63; P < 0.01) in asthmatics.

CONCLUSION AND CLINICAL RELEVANCE

CD4(+) IL-17A(+) T cells counts and serum IL-17 levels in conjunction with augmented FeNO levels are systemic markers of childhood asthma, using these markers, prediction and potential therapeutics for persistent asthmatics may be developed.

Cytokine expression in patients with bladder pain syndrome/interstitial cystitis ESSIC type 3C

PURPOSE

Bladder wall nitric oxide production in patients with bladder pain syndrome type 3C is increased compared to undetectable nitric oxide in patients with nonHunner bladder pain syndrome and healthy controls. However, the underlying mechanism/s of the increased nitric oxide production is largely unknown. We compared mRNA expression of a select group of cytokines in patients with bladder pain syndrome/interstitial cystitis type 3C and in pain-free controls.

MATERIALS AND METHODS

Cold cup biopsies from 7 patients with bladder pain syndrome type 3C and 6 healthy subjects were analyzed. mRNA expression of IL-4, 6, 10 and 17A, iNOS, TNF-α, TGF-β and IFN-γ was estimated by real-time polymerase chain reaction. IL-17 protein expression was determined by immunohistochemistry. Mast cells were labeled with tryptase to evaluate cell appearance and count.

RESULTS

IL-6, 10 and 17A, and iNOS mRNA levels as well as the number of mast cells infiltrating the bladder mucosa were significantly increased in patients with bladder pain syndrome type 3C compared to healthy controls. TNF-α, TGF-β and IFN-γ mRNA levels were similar in patients and controls. IL-17A expression at the protein level was up-regulated and localized to inflammatory cells and urothelium in patients with bladder pain syndrome type 3C.

CONCLUSIONS

Patients with bladder pain syndrome/interstitial cystitis had increased mRNA levels of IL-17A, 10 and 6, and iNOS. IL-17A might be important in the inflammatory process. To our knowledge the increase in IL-17A is a novel finding that may have new treatment implications.

Interleukin 17 contributes to the chronicity of inflammatory diseases such as rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease leading to joint destruction and bone resorption. The proinflammatory cytokine interleukin 17 (IL-17), primarily produced by Th17 cells, has been shown to be involved in all stages of the disease and to be an important contributor of RA chronicity. Three major processes drive the IL-17-mediated chronicity. Several epigenetic events, enhanced in RA patients, lead to the increased production of IL-17 by Th17 cells. IL-17 then induces the production of several inflammatory mediators in the diseased synovium, which are further synergistically enhanced via combinations of IL-17 with other cytokines. IL-17 also promotes the survival of both the synoviocytes and inflammatory cells and promotes the maturation of these immune cells. This leads to an increased number of synoviocytes and inflammatory cells in the synovial fluid and in the synovium leading to the hyperplasia and exacerbated inflammation observed in joints of RA patients. Furthermore, these IL-17-driven events initiate several feedback-loop mechanisms leading to increased expansion of Th17 cells and thereby increased production of IL-17. In this review, we aim to depict a complete picture of the IL-17-driven vicious circle leading to RA chronicity and to pinpoint the key aspects that require further exploration.

Collective nitric oxide production provides tissue-wide immunity during Leishmania infection

Nitric oxide (NO) production is critical for the host defense against intracellular pathogens; however, it is unclear whether NO-dependent control of intracellular organisms depends on cell-intrinsic or cell-extrinsic activity of NO. For example, NO production by infected phagocytes may enable these cells to individually control their pathogen burden. Alternatively, the ability of NO to diffuse across cell membranes might be critical for infection control. Here, using a murine ear infection model, we found that, during infection with the intracellular parasite Leishmania major, expression of inducible NO synthase does not confer a cell-intrinsic ability to lower parasite content. We demonstrated that the diffusion of NO promotes equally effective parasite killing in NO-producing and bystander cells. Importantly, the collective production of NO by numerous phagocytes was necessary to reach an effective antimicrobial activity. We propose that, in contrast to a cell-autonomous mode of pathogen control, this cooperative mechanism generates an antimicrobial milieu that provides the basis for pathogen containment at the tissue level.

The cytokine IL-22 promotes pathogen colonization by suppressing related commensal bacteria

Interleukin-22 (IL-22) is highly induced in response to infections with a variety of pathogens, and its main functions are considered to be tissue repair and host defense at mucosal surfaces. Here we showed that IL-22 has a unique role during infection in that its expression suppressed the intestinal microbiota and enhanced the colonization of a pathogen. IL-22 induced the expression of antimicrobial proteins, including lipocalin-2 and calprotectin, which sequester essential metal ions from microbes. Because Salmonella enterica ser. Typhimurium can overcome metal ion starvation mediated by lipocalin-2 and calprotectin via alternative pathways, IL-22 boosted its colonization of the inflamed intestine by suppressing commensal Enterobacteriaceae, which are susceptible to the antimicrobial proteins. Thus, IL-22 tipped the balance between pathogenic and commensal bacteria in favor of a pathogen. Taken together, IL-22 induction can be exploited by pathogens to suppress the growth of their closest competitors, thereby enhancing pathogen colonization of mucosal surfaces.

Common and small molecules as the ultimate regulatory and effector mediators of antigen-specific transplantation reactions

In spite of intensive research, the molecular basis of allograft and xenograft rejection still remains not fully understood. The acute rejection of an allograft is associated with the intragraft Th1 cytokine response, while tolerance of an allograft or xenograft rejection is accompanied by a higher production of the Th2 cytokines interleukin (IL)-4 and IL-10. Nevertheless, these cytokines are not the final regulatory and effector molecules mediating transplantation reactions. Data indicate that the functioning of common molecules with enzymatic activities, such are inducible nitric oxide synthase (iNOS), arginase, heme oxygenase-1 (HO-1) or indoleamine-2,3-dioxygenase (IDO), the bioavailability of their substrates (L-arginine, tryptophan, heme) and the cytotoxic and regulatory actions of their small gaseous products (NO, CO) can be the ultimate mechanisms responsible for effector or regulatory reactions. Using models of transplantation immunity and tolerance we show that T cell receptor-mediated recognition of allogeneic or xenogeneic antigens as well as the balance between immunity/tolerance induces distinct cytokine production profiles. The ratio between Th1 and Th2 cytokines efficiently regulates the expression of genes for common enzymes, such as iNOS, arginase, HO-1 and IDO. These enzymes may compete for substrates, such as L-arginine or tryptophan, and the final product of their activity are small molecules (NO, CO) displaying effector or regulatory functions of the immune system. Thus, it is suggested that in spite of the high immunological specificity of transplatation reaction, the ultimate players in regulatory and effector functions could be small and common molecules.

T helper cytokines in dry eye disease

Dry eye is an inflammatory disease that results from activation of innate inflammatory pathways in resident ocular surface cells, as well as cytokines produced by recruited T helper (Th) cells. Cytokines produced by the infiltrating Th cells alter the normal cytokine balance on the ocular surface and cause ocular surface epithelial pathology. Changes in levels of Th cytokines on the ocular surface have been measured in dry eye and the biological effects of these cytokines have been documented in experimental culture and mouse model systems. The Th2 cytokine IL-13 has a homeostatic role in promoting goblet cell differentiation. In contrast, The Th1 cytokine IFN-γ antagonizes IL-13 and promotes apoptosis and squamous metaplasia of the ocular surface epithelia. The Th17 cytokine, IL-17 promotes corneal epithelial barrier disruption. The ocular surface epithelium expresses receptors to all of these Th cytokines. Therapies that maintain normal IL-13 signaling, or suppress IFN-γ and IL-17 have potential for treating the ocular surface disease of dry eye.

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

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

Co-expression of S. Typhi GroEL and IL-22 gene augments immune responses against Salmonella infection

Recombinant DNA vaccines represent a novel method for generating in situ expression of vaccine antigens. Intramuscular injections of naked DNA are able to elicit potent humoral and cellular immune responses but still numerous factors limit the immunogenicity of DNA vaccines. Co-expression of cytokines with antigen encoding genes in DNA vectors can improve the immune responses and modify Th1/Th2 balance. In this study, the immunomodulatory effect of Interleukin 22 (IL-22) as an adjuvant was studied by DNA vaccination with S. Typhi Heat shock protein 60 (HSP60/GroEL) in mice. Further, DNA construct of IL-22 gene fused with GroEL was developed and immunization studies were carried out in mice. DNA vaccination with GroEL alone stimulated humoral and cell-mediated immune responses. Co-immunization (IL-22+GroEL) further resulted in increase in T-cell proliferative responses, antibody titres (IgG, IgG1, IgG2a) and secretion of IFNγ (Th1), IL-1β and Th2 (IL-4, IL-6) cytokines. Co-expression (IL-22-GroEL DNA) also promoted antibody titres and cytokine levels were significantly higher as compared to co-immunized group. A reduction in bacterial load in spleen, liver and intestine was seen in all the immunized groups as compared to control, with least organ burden in fusion DNA construct group (co-expression). Improved protective efficacy (90%) against lethal challenge by Salmonella was observed with IL-22-GroEL co-expressing DNA vector as compared with plasmid encoding GroEL only (50-60%) or co-immunization group (75-80%). This study thus shows that co-expression of IL-22 and GroEL genes enhances the immune responses and protective efficacy, circumventing the need of any adjuvant.

Interleukin-22 mediates early host defense against Rhizomucor pusilluscan pathogens

BACKGROUND

In recent years, the fungal infectious disease zygomycosis has increased in incidence worldwide, especially among the immunodeficient population. Despite the rates of zygomycosis-related death and deformation being very high, the mechanism(s) by which the fungal pathogens cause these severe manifestations remain unknown.

METHODS

Using the associated Rhizomucor variabilis species, which can selectively induce cutaneous zygomycosis in otherwise healthy individuals, we investigated the host mechanisms of infection-related responses, including cytokine and chemokine expression as well as contributions of particular T cell subsets. siRNA specifically targeting IL-22,IL-17 and IFN-γ were used to down-regulate expression of those molecules.

RESULTS

In mouse models of infection, IL-22 was implicated in development of Rhizomucor spp.-induced skin lesions. In cultured human peripheral blood monocytes, R. pusilluscan, which is often found in immunodeficient patients, induced the production of IL-22, while R. variabilis did not. Moreover, Rhizomucor spp.-induced secretion of Il-22 from CCR6(+)CCR4(+)CCR10(+) cells was down-regulated by knockdown of IL-22 related signaling receptors, RORC and ARH.

CONCLUSION

Our data strongly suggest that avoidance of IL-22 may be one mechanism by which mucor species produce morbidity and mortality in infected individuals.

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.

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.

IL-36γ/IL-1F9, an innate T-bet target in myeloid cells

By concerted action in dendritic (DC) and T cells, T-box expressed in T cells (T-bet, Tbx21) is pivotal for initiation and perpetuation of Th1 immunity. Identification of novel T-bet-regulated genes is crucial for further understanding the biology of this transcription factor. By combining siRNA technology with genome-wide mRNA expression analysis, we sought to identify new T-bet-regulated genes in predendritic KG1 cells activated by IL-18. One gene robustly dependent on T-bet was IL-36γ, a recently described novel IL-1 family member. Promoter analysis revealed a T-bet binding site that, along with a κB site, enables efficient IL-36γ induction. Using knock-out animals, IL-36γ reliance on T-bet was extended to murine DC. IL-36γ expression by human myeloid cells was confirmed using monocyte-derived DC and M1 macrophages. The latter model was employed to substantiate dependence of IL-36γ on endogenous T-bet in human primary cells. Ectopic expression of T-bet likewise mediated IL-36γ production in HaCaT keratinocytes that otherwise lack this transcription factor. Additional experiments furthermore revealed that mature IL-36γ has the capability to establish an inflammatory gene expression profile in human primary keratinocytes that displays enhanced mRNA levels for TNFα, CCL20, S100A7, inducible NOS, and IL-36γ itself. Data presented herein shed further light on involvement of T-bet in innate immunity and suggest that IL-36γ, besides IFNγ, may contribute to functions of this transcription factor in immunopathology.