Novel approach for interleukin-23 up-regulation in human dendritic cells and the impact on T helper type 17 generation

Psoriatic skin inflammation is promoted by c-Jun/AP-1-dependent CCL2 and IL-23 expression in dendritic cells

Toll‐like receptor (TLR) stimulation induces innate immune responses involved in many inflammatory disorders including psoriasis. Although activation of the AP‐1 transcription factor complex is common in TLR signaling, the specific involvement and induced targets remain poorly understood. Here, we investigated the role of c‐Jun/AP‐1 protein in skin inflammation following TLR7 activation using human psoriatic skin, dendritic cells (DC), and genetically engineered mouse models. We show that c‐Jun regulates CCL2 production in DCs leading to impaired recruitment of plasmacytoid DCs to inflamed skin after treatment with the TLR7/8 agonist Imiquimod. Furthermore, deletion of c‐Jun in DCs or chemical blockade of JNK/c‐Jun signaling ameliorates psoriasis‐like skin inflammation by reducing IL‐23 production in DCs. Importantly, the control of IL‐23 and CCL2 by c‐Jun is most pronounced in murine type‐2 DCs. CCL2 and IL‐23 expression co‐localize with c‐Jun in type‐2/inflammatory DCs in human psoriatic skin and JNK‐AP‐1 inhibition reduces the expression of these targets in TLR7/8‐stimulated human DCs. Therefore, c‐Jun/AP‐1 is a central driver of TLR7‐induced immune responses by DCs and JNK/c‐Jun a potential therapeutic target in psoriasis.

Severe depletion of peripheral blood dendritic cell subsets in obstructive sleep apnea patients: A new link with cancer?

Recent evidence suggests that alterations of the immune responses are associated with the inflammatory nature of obstructive sleep apnea (OSA) and of its related co-morbidities. In this scenario, we asked whether circulating dendritic cell (DC) subsets may be possible players as their role has not yet been detailed. The frequency distribution of peripheral blood myeloid (mDC1 and mDC2) and plasmacytoid (p) DCs was investigated by mean of multi-parametric flow cytometry in 45 OSA patients (mean age: 53 yrs; M = 29) at the time of the first diagnosis and compared to 30 age- and sex-matched healthy controls. Oxidative burst (OB) and serum levels of tumor necrosis factor (TNF)-α, (interleukin) (IL)-6, interferon (INF)-γ, IL-2, IL-4, IL-10 and vascular endothelial growth factor (VEGF) were also analyzed. All subsets of circulating DCs were significantly depleted in OSA patients as compared to healthy subjects (p < 0.01, in all instances), with mDC2 and pDC subtypes being more severely compromised. These findings were co-existing with higher levels of OB along with an increased expression of IL-6, IL-10, TNF-α, IFN-γ, and VEGF (p < 0.005 in all instances). In particular, IL6 levels were significantly higher (p = 0.013) in severe OSA patients (apnea/hypopnea index >30) and were inversely correlated with both mDC2 (r = -0.802, p < 0.007) and pDC (r = -0.317, p = 0.04) subsets. We first provide evidence for a constitutive reduction of all circulating DC subsets in OSA patients. Perturbation of DCs coexists with an inflammatory milieu and is negatively correlated with the expression of IL-6, which is actually recognized as a pivotal inhibitor of DC maturation. Future studies exploring the contribution of DCs in the pathogenesis of OSA and of its complications should be encouraged.

Determination of IL-23 Pharmacokinetics by Highly Sensitive Accelerator Mass Spectrometry and Subsequent Modeling to Project IL-23 Suppression in Psoriasis Patients Treated with Anti-IL-23 Antibodies

The pro-inflammatory cytokine interleukin (IL)-23 is a key modulator of the immune response, making it an attractive target for the treatment of autoimmune disease. Correspondingly, several monoclonal antibodies against IL-23 are either in development or approved for autoimmune indications such as psoriasis. Despite being a clinical validated target, IL-23 pharmacokinetics (e.g., IL-23 synthesis and elimination rates) and the degree of target suppression (i.e., decrease in free "active" IL-23) associated with clinical efficacy are not well understood, primarily due to its ultra-low circulating levels and the lack of sensitive and accurate measurement methods. In the current work, this issue was overcome by using accelerator mass spectrometry (AMS) to measure the concentration and pharmacokinetics of human recombinant [¹⁴C]-IL-23 following an intravenous trace-dose in cynomolgus monkeys. IL-23 pharmacokinetic parameters along with clinical drug exposure and IL-23 binding affinities from four different anti-IL-23 antibodies (ustekinumab, tildrakizumab, guselkumab, and risankizumab) were used to build a pharmacokinetics/pharmacodynamics (PK/PD) model to assess the time course of free IL-23 over one year in psoriasis patients following different dosing regimens. The predicted rank order of reduction of free IL-23 was consistent with their reported rank order of Psoriasis Area and Severity Index (PASI) 100 scores in clinical efficacy trials (ustekinumab < tildrakizumab < guselkumab < risankizumab), thus demonstrating the utility of highly sensitive AMS for determining target pharmacokinetics to inform PK/PD modeling and assessing target suppression associated with clinical efficacy.

Identification of CD37, cystatin A, and IL-23A gene expression in association with brain metastasis: analysis of a prospective trial

PURPOSE/OBJECTIVES

We aimed to assess the predictive value of a lung cancer gene panel for the development of brain metastases.

MATERIALS/METHODS

Between 2011 and 2015, 102 patients with lung cancer were prospectively enrolled in a clinical trial in which a diagnostic fine-needle aspirate was obtained. Gene expression was conducted on all samples that rendered a diagnosis of non-small cell lung cancer (NSCLC). Subsequent retrospective analysis of brain metastases-related outcomes was performed by reviewing patient electronic medical records. A competing risk multivariable regression was performed to estimate the adjusted hazard ratio for the development of brain metastases and non-brain metastases from NSCLC.

RESULTS

A total of 49 of 102 patients had died by the last follow-up. Median time of follow-up was 13 months (range 0.23-67 months). A total of 17 patients developed brain metastases. Median survival time after diagnosis of brain metastases was 3.58 months (95% confidence interval (CI) 2.17, not available). A total of 30 patients developed metastases without any evidence of brain metastases until the time of death or last follow-up. Competing risk analysis identified three genes that were downregulated differentially in the patients with brain metastases versus non-brain metastatic disease: CD37 (0.017), cystatin A (0.022), and IL-23A (0.027). Other factors associated with brain metastases include: stage T ( P ⩽ 8.3e-6) and stage N ( P= 6.8e-4).

CONCLUSIONS

We have identified three genes, CD37, cystatin A, and IL-23A, for which downregulation of gene expression was associated with a greater propensity for developing brain metastases. Validation of these biomarkers could have implications on surveillance patterns in patients with brain metastases from NSCLC.

Altered Immune Activation and IL-23 Signaling in Response to Candida albicans in Autoimmune Polyendocrine Syndrome Type 1

OBJECTIVE

Autoimmune polyendocrine syndrome type 1 (APS-1) is a rare, childhood onset disease caused by mutations in the autoimmune regulator (AIRE) gene. Chronic mucocutaneous candidiasis (CMC) is one of the three major disease components and is, to date, mainly explained by the presence of neutralizing auto-antibodies against cytokines [interleukin (IL)-17A, IL-17F, and IL-22] from T helper 17 cells, which are critical for the protection against fungal infections. However, patients without current auto-antibodies also present CMC and we, therefore, hypothesized that other immune mechanisms contribute to CMC in APS-1.

METHODS

Whole blood was stimulated with Candida albicans (C. albicans) in a standardized assay, and immune activation was investigated by analyzing 46 secreted immune mediators. Then, peripheral blood mononuclear cells were stimulated with curdlan, a Dectin-1 agonist and IL-23 inducer, and the IL-23p19 response in monocytes was analyzed by flow cytometry.

RESULTS

We found an altered immune response in APS-1 patients compared with healthy controls. Patients fail to increase the essential ILs, such as IL-2, IL-17A, IL-22, and IL-23, when stimulating whole blood with C. albicans. A significantly altered IL-23p19 response was detected in patients' monocytes upon stimulation with curdlan.

CONCLUSION

APS-1 patients have an altered immune response to C. albicans including a dysregulation of IL-23p19 production in monocytes. This probably contributes to the selective susceptibility to CMC found in the majority of patients.

Interleukin-23 mediates the pathogenesis of LPS/GalN-induced liver injury in mice

BACKGROUND

Interleukin-23 (IL-23) is required for T helper 17 (Th17) cell responses and IL-17 production in hepatitis B virus infection. A previous study showed that the IL-23/IL-17 axis aggravates immune injury in patients with chronic hepatitis B virus infection. However, the role of IL-23 in acute liver injury remains unclear.

OBJECTIVE

The purpose of this study was to determine the role of the inflammatory cytokine IL-23 in lipopolysaccharide/d-galactosamine (LPS/GalN)-induced acute liver injury in mice.

METHODS

Serum IL-23 from patients with chronic hepatitis B virus (CHB), acute-on-chronic liver failure (ACLF) and healthy individuals who served as healthy controls (HCs) was measured by ELISA. An IL-23p19 neutralizing antibody or an IL-23p40 neutralizing antibody was administered intravenously at the time of challenge with LPS (10μg/kg) and GalN (400mg/kg) in C57BL/6 mice. Hepatic pathology and the expression of Th17-related cytokines, including IL-17 and TNF-α; neutrophil chemoattractants, including Cxcl1, Cxcl2, Cxcl9, and Cxcl10; and the stabilization factor Csf3 were assessed in liver tissue.

RESULTS

Serum IL-23 was significantly upregulated in ACLF patients compared with CHB patients and HCs (P<0.05 for both). Serum IL-23 was significantly upregulated in the non-survival group compared with the survival group of ACLF patients, which was consistent with LPS/GalN-induced acute hepatic injury in mice (P<0.05 for both). Moreover, after treatment, serum IL-23 was downregulated in the survival group of ACLF patients (P<0.001). Compared with LPS/GalN mice, mice treated with either an IL-23p19 neutralizing antibody or an IL-23p40 neutralizing antibody showed less severe liver tissue histopathology and significant reductions in the expression of Th17-related inflammatory cytokine, including IL-17 and TNF-α; neutrophil chemoattractants, including Cxcl1, Cxcl2, Cxcl9, and Cxcl10; and stabilization factors Csf3 within the liver tissue compared with LPS/GalN mice (P<0.05 for all).

CONCLUSION

High serum IL-23 was associated with mortality in ACLF patients and LPS/GalN-induced acute liver injury in mice. IL-23 neutralizing antibodies attenuated liver injury by reducing the expression of Th17-related inflammatory cytokines, neutrophil chemoattractants and stabilization factors within the liver tissue, which indicated that IL-23 likely functions upstream of Th17-related cytokine and chemokine expression to recruit inflammatory cells into the liver.

Lipopolysaccharide-Mediated Induction of Concurrent IL-1β and IL-23 Expression in THP-1 Cells Exhibits Differential Requirements for Caspase-1 and Cathepsin B Activity

The inflammasome is a multimeric protein complex required for interleukin (IL)-1β production. Upon lipopolysaccharide (LPS) triggering of toll-like receptor (TLR)-4 and subsequent ATP signaling, the NOD-like receptor containing-pyrin domain 3 (NLRP3) inflammasome is activated to cleave pro-caspase-1 into caspase-1, allowing the secretion of IL-1β. IL-1β is known to function with IL-23 in the regulation of IL-17-producing CD4(+) T cells, Th17 cells, in adaptive immunity. Recently, studies have shown that IL-1β and IL-23 together activate IL-17-producing innate lymphoid cells, demonstrating that the pair may exhibit additional effects on cell differentiation. Using an in vitro model of bacterial infection, LPS treatment of human monocytic cells, we investigated the molecular mechanisms involved in the co-expression of IL-1β and IL-23. We found that IL-1β is partially required for optimal LPS-induced IL-23 production. We also found that IL-23 production was partially dependent on ATP signaling via the P2X7 receptor, whereas IL-1β production required this signaling. Furthermore, we identified a novel role for cathepsin B activity in IL-23 production. Taken together, this study identifies differential requirements for the co-expression of IL-1β and IL-23. Due to their similar roles in Th17 differentiation, characterization of the regulatory mechanisms for LPS-induced IL-1β and IL-23 may reveal novel information into the pathology of the inflammatory response particularly during bacterial infection.

Stromal fibroblasts support dendritic cells to maintain IL-23/Th17 responses after exposure to ionizing radiation

Cross talk between DCs and FBs in understanding the effects of IR in DC function.

Dendritic cell function is modulated by stromal cells, including fibroblasts. Although poorly understood, the signals delivered through this crosstalk substantially alter dendritic cell biology. This is well illustrated with release of TNF-α/IL-1β from activated dendritic cells, promoting PGE₂ secretion from stromal fibroblasts. This instructs dendritic cells to up-regulate IL-23, a key Th17-polarizing cytokine. We previously showed that ionizing radiation inhibited IL-23 production by human dendritic cells in vitro. In the present study, we investigated the hypothesis that dendritic cell-fibroblast crosstalk overcomes the suppressive effect of ionizing radiation to support appropriately polarized Th17 responses. Radiation (1–6 Gy) markedly suppressed IL-23 secretion by activated dendritic cells (P < 0.0001) without adversely impacting their viability and consequently, inhibited the generation of Th17 responses. Cytokine suppression by ionizing radiation was selective, as there was no effect on IL-1β, -6, -10, and -27 or TNF-α and only a modest (11%) decrease in IL-12p70 secretion. Coculture with fibroblasts augmented IL-23 secretion by irradiated dendritic cells and increased Th17 responses. Importantly, in contrast to dendritic cells, irradiated fibroblasts maintained their capacity to respond to TNF-α/IL-1β and produce PGE₂, thus providing the key intermediary signals for successful dendritic cell-fibroblasts crosstalk. In summary, stromal fibroblasts support Th17-polarizing cytokine production by dendritic cells that would otherwise be suppressed in an irradiated microenvironment. This has potential ramifications for understanding the immune response to local radiotherapy. These findings underscore the need to account for the impact of microenvironmental factors, including stromal cells, in understanding the control of immunity.

Interleukin 23 regulates the functions of human decidual immune cells during early pregnancy

BACKGROUND

This study investigated the effects of interleukin 23 (IL-23) on the production of cytokines (IL-1, IL-4, IL-10, and IL-17), the differentiation of Treg/Th17 and STAT3 (i.e., signal transducer and activator of transcription 3) in human decidual immune cells (DICs) during early pregnancy.

METHODS

DICs were treated with recombinant human IL-23 and an antibody against IL-23 subunit p19. The differentiation of Treg and Th17 cells was detected by flow cytometry. Levels of IL-23 receptor (IL-23R), STAT3, and phosphorylated STAT3 (pSTAT3) was examined by Western blot. The production of IL1, IL4, IL10, and IL-17 in DICs was measured by ELISA.

RESULTS

Exogenous recombinant human IL-23 significantly promoted the differentiation of Th17 cells from DICs, while anti-IL-23 antibody significantly promoted the differentiation of Treg cells from DICs. Consistent with the differentiation of Th17 and Tregs cells, levels of IL-1β and IL-17 correlated positively with IL-23 treatment, and anti-IL-23 antibody increased the secretion of IL-4 and IL-10 from DICs. Levels of pSTAT3, but not STAT3 or IL-23R, were significantly elevated by recombinant IL-23 treatment; anti-IL-23 antibody significantly decreased the levels of pSTAT3 and IL-23R in DICs.

CONCLUSIONS

IL-23 mediates the differentiation of Th17 and Treg cells and the production of associated cytokines in DICs. The potential mechanism likely involves the STAT3 pathway.

T-helper 17 cell polarization in pulmonary arterial hypertension

BACKGROUND

Inflammation may contribute to the pathobiology of pulmonary arterial hypertension (PAH). Deciphering the PAH fingerprint on the inflammation orchestrated by dendritic cells (DCs) and T cells, key driver and effector cells, respectively, of the immune system, may allow the identification of immunopathologic approaches to PAH management.

METHODS

Using flow cytometry, we performed immunophenotyping of monocyte-derived DCs (MoDCs) and circulating lymphocytes from patients with idiopathic PAH and control subjects. With the same technique, we performed cytokine profiling of both populations following stimulation, coculture, or both. We tested the immunomodulatory effects of a glucocorticoid (dexamethasone [Dex]) on this immunophenotype and cytokine profile. Using an epigenetic approach, we confirmed the immune polarization in blood DNA of patients with PAH.

RESULTS

The profile of membrane costimulatory molecules of PAH MoDCs was similar to that of control subjects. However, PAH MoDCs retained higher levels of the T-cell activating molecules CD86 and CD40 after Dex pretreatment than did control MoDCs. This was associated with an increased expression of IL-12p40 and a reduced migration toward chemokine (C-C motif) ligand 21. Moreover, both with and without Dex, PAH MoDCs induced a higher activation and proliferation of CD4+ T cells, associated with a reduced expression of IL-4 (T helper 2 response) and a higher expression of IL-17 (T helper 17 response). Purified PAH CD4+ T cells expressed a higher level of IL-17 after activation than did those of control subjects. Lastly, there was significant hypomethylation of the IL-17 promoter in the PAH blood DNA as compared with the control blood.

CONCLUSIONS

We have highlighted T helper 17 cell immune polarization in patients with PAH, as has been previously demonstrated in other chronic inflammatory and autoimmune conditions.

The serum IL-23 level predicts the response to pegylated interferon therapy in patients with chronic hepatitis B

BACKGROUND & AIMS

This study investigated the possible use of interleukin (IL)-23 and IL-17 serum levels as indicators for anti-hepatitis B virus (HBV) therapy.

METHODS

A total of 127 patients with chronic hepatitis B (CHB) who received pegylated interferon (PegIFN) therapy, 20 chronic asymptomatic HBV carriers (AsCs) and 32 healthy controls were recruited. The serum levels of IL-23 and IL-17 were detected by ELISA. The predictive value of baseline and early on-treatment changes in the levels of IL-23 and IL-17 for therapeutic response were evaluated by receiver operating characteristic analysis. Multivariate logistic regression models were generated to identify independent factors that affect the clearance of hepatitis B e antigen (HBeAg) and the decline in hepatitis B surface antigen (HBsAg).

RESULTS

The baseline serum levels of IL-23 and IL-17 were higher in patients with CHB than in normal controls and in AsCs. High levels of pre-treatment IL-23 and IL-17 and more significant on-treatment reductions in IL-23 and IL-17 levels were observed in patients with CHB who achieved HBeAg clearance or a decline in HBsAg >1 log10  IU/ml compared with patients who were persistently HBeAg-positive or who experienced a decline in HBsAg <1 log10  IU/ml. The predictive cut-off value of IL-23 for HBeAg clearance was 135 pg/ml, and the specificity and sensitivity were 71.4% and 70% respectively. A high pre-treatment level of IL-23 was an independent factor for the prediction of the therapeutic response in patients with HBeAg-positive CHB. Early on-treatment changes of IL-23 and IL-17 showed no predictive value.

CONCLUSIONS

A high pre-treatment serum IL-23 level predicts the therapeutic response in HBeAg-positive CHB patients during PegIFN therapy.

Engagement of Toll-like receptor 2 enhances interleukin (IL)-17(+) autoreactive T cell responses via p38 mitogen-activated protein kinase signalling in dendritic cells

Functional analysis of single Toll-like receptors (TLRs) in vivo is necessary to understand how they shape the ocular inflammation involved in uveitis. In this study we explored the role and mechanisms of TLR-2 agonists on the autoreactive T helper type 17 (Th17) response in experimental autoimmune uveitis (EAU). Treatment by peptidoglycan (PGN), a specific TLR-2 agonist, remarkably increased mRNA levels of Th17-lineage genes interleukin (IL)-17A, IL-21 and RAR-related orphan receptor (ROR)γt and promoted antigen-specific Th17 response in EAU mice. A mixture of PGN and interphotoreceptor retinoid-binding protein peptide (IRBP161-180 ) could effectively induce EAU in the absence of complete Freund's adjuvant (CFA). PGN treatment also enhanced the pathogenic activities of activated antigen-specific Th17 cells in vivo. PGN significantly increased the production of IL-1β, IL-6 and IL-23 of dendritic cells (DCs) and enhanced their ability to promote IL-17(+) uveitogenic T cells. Enhanced immunostimulatory activities of PGN-DCs depend upon p38 activation. Inhibition of p38 mitogen-activated protein kinase (MAPK) activity dramatically decreased IL-17 gene expression and antigen-specific Th17 responses stimulated by PGN-DCs. Our findings suggest that PGN treatment dramatically promotes the IL-17(+) uveitogenic T cell responses via enhancing the immunostimulatory activities of DCs. This effect may be mediated, at least in part, by activation of the p38 signalling pathway in DCs.

Novel function for the p38-MK2 signaling pathway in circulating CD1c+ (BDCA-1+) myeloid dendritic cells from healthy donors and advanced cancer patients; inhibition of p38 enhances IL-12 whilst suppressing IL-10

There is growing interest in myeloid (my) dendritic cells (DC) as an alternative to monocyte-derived DC (moDC) for immunotherapy. However, in contrast to moDC, little is known regarding the effect of malignancy on the function, abundance or use of intracellular signaling pathways in myDC. Understanding the molecular detail of circulating myDC is therefore important for future use in advanced cancer. Advanced cancer patients had similar numbers of circulating myDC to cancer-free patients and healthy individuals, and secreted similar levels of IL-1β, IL-6, IL-10, IL-12 and IL-23. However, myDC from some patients failed to secrete the Th1-cytokine IL-12. Surprisingly, inhibiting p38 (p38i) signaling (using BIRB0796 or SB203580) markedly increased IL-12 secretion by myDC. This is in complete contrast to what is established for moDC where inhibiting p38 ablates IL-12. Interestingly, this was specific to IL-12, since IL-10 was suppressed by p38i in both DC types. The opposing effect of p38i on IL-12 was evident at the transcriptional level and in both DC types was mediated through the p38-MK2 pathway but did not involve differential phosphorylation of the distal Rsk kinase. Importantly, where patient myDC did not secrete IL-12 (or after treatment with suppressive melanoma lysate), p38i restored IL-12 to normal levels. In contrast to p38, inhibiting the other MAPK pathways had similar consequences in both DC types. We show for the first time the differential use of a major intracellular signaling pathway by myDC. Importantly, there are sufficient circulating myDC in advanced cancer patients to consider development of adoptive immunotherapy.

Involvement of levels of Toll like receptor-4 in monocytes, CD4+ T-lymphocyte subsets, and cytokines in patients with immune thrombocytopenic purpura

INTRODUCTION

Toll-like receptors have been found to be associated with immune-mediated diseases but it is still not clear whether they play a role in immune thrombocytopenic purpura (ITP), especially TLR4. CD4+ T-lymphocyte abnormalities, including Th17, Th1, Th2, and regulator T cell (Treg), are considered important in ITP. There have been few studies regarding the expression of TLR4 and the relationships between TLR4 and Th17 levels in ITP.

MATERIALS AND METHODS

In this study, we evaluated the expression of TLR4 in monocytes, the plasma concentrations of IL-23, IL-17 and the profiles of Th17, Th1, Th2 cells in 70 patients with ITP and 31 healthy controls. In addition, we evaluated IL-2 and Treg cells in 46 cases of 70 patients with ITP and the same 31 controls.

RESULTS

Higher levels of TLR4 expression, higher relative numbers of Th17 and Th1 cells and lower levels of Treg cells were observed in patients when compared with controls (p=0.001 for TLR4; p<0.001 for Th17; p=0.014 for Th1; p=0.001 for Treg). The levels of IL-23 and IL-2 were increased (p=0.022 for IL-23; p=0.025 for IL-2), the relative levels of Th2 and concentrations of IL-17 were similar across both groups (p=0.446 for Th2; p=0.316 for IL-17). A significant negative correlation was observed between levels of TLR4 and Treg(r=-0.544, p<0.001), but a significantly positive correlation was observed between IL-2 and IL-23 concentration in patients (r=0.441, p=0.004). Neither the correlation between TLR4 and the other CD4(+) T cells and cytokines nor the correlation between the three cytokines and CD4+ T cells was found to be statistically significant.

CONCLUSIONS

Our data showed that TLR4, CD4+ T cells (Th1, Th17 and Treg cells) and related cytokines (IL-23, IL-2) may take part in the pathogenesis of ITP. TLR4 may play a role through the TLR4-cytokine-CD4+ T lymphocyte cell pathway.

Therapeutic potency of Poly I:C in HSV-induced inflammation through up-regulation of IL-15 receptor alpha

Interleukin-15 receptor alpha (IL-15Rα) forms stable complex with IL-15 on the cell surface of activated monocytes and mediates the proliferation of memory CD8+ T cells. Recent studies informed that polyinosinic:polycytidylic acid (Poly I:C) is an immunostimulant which boosts the generation of memory T cells through induction of IL-15Rα. The aim of this study is to evaluate the relevance of IL-15Rα in Herpes simplex virus (HSV)-induced Behçet's disease (BD) mouse model and BD patients. The frequencies of IL-15Rα expression in PBMCs of BD patients and BD-like symptomatic mice were analyzed by flow cytometry. In addition, Poly I:C supplementation could reduce inflammation through the up-regulation of memory T cells and IL-15Rα+ cells accompany with down-regulation of pro-inflammatory cytokine, IL-17A in BD mice. In BD patients, the frequencies of IL-15Rα expression in PBMCs were also significantly different between the inactive and active disease states. These results suggest that IL-15Rα is a relevant factor in BD.

IL-23/IL-17A axis correlates with the nitric oxide pathway in inflammatory bowel disease: immunomodulatory effect of retinoic acid

Inflammatory bowel diseases (IBDs) are chronic inflammatory diseases of the gastrointestinal tract, which are clinically present as 1 of the 2 disorders, Crohn's disease (CD) or ulcerative colitis (UC) (Rogler 2004). The immune dysregulation in the intestine plays a critical role in the pathogenesis of IBD, involving a wide range of molecules, including cytokines. The aim of this work was to study the involvement of T-helper 17 (Th17) subset in the bowel disease pathogenesis by the nitric oxide (NO) pathway in Algerian patients with IBD. We investigated the correlation between the proinflammatory cytokines [(interleukin (IL)-17, IL-23, and IL-6] and NO production in 2 groups of patients. We analyzed the expression of messenger RNAs (mRNAs) encoding Th17 cytokines, cytokine receptors, and NO synthase 2 (NOS2) in plasma of the patients. In the same way, the expression of p-signal transducer and activator of transcription 3 (STAT3) and NOS2 was measured by immunofluorescence and immunohistochemistry. We also studied NO modulation by proinflammatory cytokines (IL-17A, IL-6, tumor necrosis factor α, or IL-1β) in the presence or absence of all-trans retinoic acid (At RA) in peripheral blood mononuclear cells (PBMCs), monocytes, and in colonic mucosa cultures. Analysis of cytokines, cytokine receptors, and NOS2 transcripts revealed that the levels of mRNA transcripts of the indicated genes are elevated in all IBD groups. Our study shows a significant positive correlation between the NO and IL-17A, IL-23, and IL-6 levels in plasma of the patients with IBD. Interestingly, the correlation is significantly higher in patients with active CD. Our study shows that both p-STAT3 and inducible NOS expression was upregulated in PBMCs and colonic mucosa, especially in patients with active CD. At RA downregulates NO production in the presence of proinflammatory cytokines for the 2 groups of patients. Collectively, our study indicates that the IL-23/IL-17A axis plays a pivotal role in IBD pathogenesis through the NO pathway.

The ataxia telangiectasia mutated kinase pathway regulates IL-23 expression by human dendritic cells

Little is known of the regulation of IL-23 secretion in dendritic cells (DC) despite its importance for human Th17 responses. In this study, we show for first time, to our knowledge, that the ataxia telangiectasia mutated (ATM) pathway, involved in DNA damage sensing, acts as an IL-23 repressor. Inhibition of ATM with the highly selective antagonist KU55933 markedly increased IL-23 secretion in human monocyte-derived DC and freshly isolated myeloid DC. In contrast, inhibiting the closely related mammalian target of rapamycin had no effect on IL-23. Priming naive CD4(+) T cells with ATM-inhibited DC increased Th17 responses over and above those obtained with mature DC. Although ATM blockade increased the abundance of p19, p35, and p40 mRNA, IL-12p70 secretion was unaffected. To further examine a role for ATM in IL-23 regulation, we exposed DC to low doses of ionizing radiation. Exposure of DC to x-rays resulted in ATM phosphorylation and a corresponding depression of IL-23. Importantly, ATM inhibition with KU55933 prevented radiation-induced ATM phosphorylation and abrogated the capacity of x-rays to suppress IL-23. To explore how ATM repressed IL-23, we examined a role for endoplasmic reticulum stress responses by measuring generation of the spliced form of X-box protein-1, a key endoplasmic reticulum stress transcription factor. Inhibition of ATM increased the abundance of X-box protein-1 mRNA, and this was followed 3 h later by increased peak p19 transcription and IL-23 release. In summary, ATM activation or inhibition, respectively, inhibited or augmented IL-23 release. This novel role of the ATM pathway represents a new therapeutic target in autoimmunity and vaccine development.

Autophagy regulates IL-23 secretion and innate T cell responses through effects on IL-1 secretion

Autophagy controls IL-1β secretion by regulating inflammasome activation and by targeting pro-IL-1β for degradation. In this article, we show that inhibition of autophagy, either with the PI3K inhibitors 3-methyladenine, wortmannin, and LY294002 or with small interfering RNA against autophagy proteins augmented the secretion of IL-23 by human and mouse macrophages and dendritic cells in response to specific TLR agonists. This process occurred at the transcriptional level and was dependent on reactive oxygen species and IL-1R signaling; it was abrogated with an IL-1R antagonist or with IL-1-neutralizing Abs, whereas treatment with either rIL-1α or IL-1β induced IL-23 secretion. Dendritic cells treated with LPS and 3-methyladenine secreted enhanced levels of both IL-1β and IL-23, and supernatants from these cells stimulated the innate secretion of IL-17, IFN-γ, and IL-22 by γδ T cells. These data demonstrate that autophagy has a potentially pivotal role to play in the induction and regulation of inflammatory responses by innate immune cells, largely driven by IL-1 and its consequential effects on IL-23 secretion.

Interleukin-23: as a drug target for autoimmune inflammatory diseases

Interleukin-23 (IL-23) is a member of the IL-12 family of cytokines with pro-inflammatory properties. Its ability to potently enhance the expansion of T helper type 17 (Th17) cells indicates the responsibility for many of the inflammatory autoimmune responses. Emerging data demonstrate that IL-23 is a key participant in central regulation of the cellular mechanisms involved in inflammation. Both IL-23 and IL-17 form a new axis through Th17 cells, which has evolved in response to human diseases associated with immunoactivation and immunopathogeny, including bacterial or viral infections and chronic inflammation. Targeting of IL-23 or the IL-23 receptor or IL-23 axis is a potential therapeutic approach for autoimmune diseases including psoriasis, inflammatory bowel disease, rheumatoid arthritis and multiple sclerosis. The current review focuses on the immunobiology of IL-23 and summarizes the most recent findings on the role of IL-23 in the pre-clinical and ongoing clinical studies.