Suppression of TNF-α and IL-1 signaling identifies a mechanism of homeostatic regulation of macrophages by IL-27

IL-27 is a pleiotropic cytokine with both activating and inhibitory functions on innate and acquired immunity. IL-27 is expressed at sites of inflammation in cytokine-driven autoimmune/inflammatory diseases, such as rheumatoid arthritis, psoriasis, inflammatory bowel disease, and sarcoidosis. However, its role in modulating disease pathogenesis is still unknown. In this study, we found that IL-27 production is induced by TNF-α in human macrophages (MΦ) and investigated the effects of IL-27 on the responses of primary human MΦ to the endogenous inflammatory cytokines TNF-α and IL-1. In striking contrast to IL-27-mediated augmentation of TLR-induced cytokine production, we found that IL-27 suppressed MΦ responses to TNF-α and IL-1β, thus identifying an anti-inflammatory function of IL-27. IL-27 blocked the proximal steps of TNF-α signaling by downregulating cell-surface expression of the signaling receptors p55 and p75. The mechanism of inhibition of IL-1 signaling was downregulation of the ligand-binding IL-1RI concomitant with increased expression of the receptor antagonist IL-1Ra and the decoy receptor IL-1RII. These findings provide a mechanism for suppressive effects of IL-27 on innate immune cells and suggest that IL-27 regulates inflammation by limiting activation of MΦ by inflammatory cytokines while preserving initial steps in host defense by augmenting responses to microbial products.     

Joint production of IL-22 participates in the initial phase of antigen-induced arthritis through IL-1β production

IntroductionRheumatoid arthritis (RA) is a chronic autoimmune disease characterized by neutrophil articular infiltration, joint pain and the progressive destruction of cartilage and bone. IL-22 is a key effector molecule that plays a critical role in autoimmune diseases. However, the function of IL-22 in the pathogenesis of RA remains controversial. In this study, we investigated the role of IL-22 in the early phase of antigen-induced arthritis (AIA) in mice.MethodsAIA was induced in C57BL/6, IL-22^−/−, ASC^−/− and IL-1R1^−/− immunized mice challenged intra-articularly with methylated bovine serum albumin (mBSA). Expression of IL-22 in synovial membranes was determined by RT-PCR. Articular hypernociception was evaluated using an electronic von Frey. Neutrophil recruitment and histopathological analyses were assessed in inflamed knee joint. Joint levels of inflammatory mediators and mBSA-specific IgG concentration in the serum were measured by ELISA.ResultsThe IL-22 mRNA expression and protein levels in synovial tissue were increased during the onset of AIA. In addition, pharmacological inhibition (anti-IL-22 antibody) and genetic deficiency (IL-22^−/− mice) reduced articular pain and neutrophil migration in arthritic mice. Consistent with these findings, recombinant IL-22 joint administration promoted articular inflammation per se in WT mice, restoring joint nociception and neutrophil infiltration in IL-22^−/− mice. Moreover, IL-22-deficient mice showed reduced synovitis (inflammatory cell influx) and lower joint IL-1β levels, whereas the production of IL-17, MCP-1/CCL2, and KC/CXCL1 and the humoral immune response were similar, compared with WT mice. Corroborating these results, the exogenous administration of IL-22 into the joints induced IL-1β production in WT mice and reestablished IL-1β production in IL-22^−/− mice challenged with mBSA. Additionally, IL-1R1^−/− mice showed attenuated inflammatory features induced by mBSA or IL-22 challenge. Articular nociception and neutrophil migration induced by IL-22 were also reduced in ASC^−/− mice.ConclusionsThese results suggest that IL-22 plays a pro-inflammatory/pathogenic role in the onset of AIA through an ASC-dependent stimulation of IL-1β production.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0759-2) contains supplementary material, which is available to authorized users.     

The p38 MAPK Regulates IL-24 Expression by Stabilization of the 3′ UTR of IL-24 mRNA

Background

IL-24 (melanoma differentiation-associated gene-7 (mda-7)), a member of the IL-10 cytokine family, possesses the properties of a classical cytokine as well as tumor suppressor effects. The exact role of IL-24 in the immune system has not been defined but studies have indicated a role for IL-24 in inflammatory conditions such as psoriasis. The tumor suppressor effects of IL-24 include inhibition of angiogenesis, sensitization to chemotherapy, and p38 mitogen-activated protein kinase (MAPK)-mediated apoptosis. Current knowledge on the regulation of IL-24 expression is sparse. Previous studies have suggested that mRNA stabilization is of major importance to IL-24 expression. Yet, the mechanisms responsible for the regulation of IL-24 mRNA stability remain unidentified. As p38 MAPK is known to regulate gene expression by interfering with mRNA degradation we examined the role of p38 MAPK in the regulation of IL-24 gene expression in cultured normal human keratinocytes.

Methodology/Principal Findings

In the present study we show that anisomycin- and IL-1β- induced IL-24 expression is strongly dependent on p38 MAPK activation. Studies of IL-24 mRNA stability in anisomycin-treated keratinocytes reveal that the p38 MAPK inhibitor SB 202190 accelerates IL-24 mRNA decay suggesting p38 MAPK to regulate IL-24 expression by mRNA-stabilizing mechanisms. The insertion of the 3′ untranslated region (UTR) of IL-24 mRNA in a tet-off reporter construct induces degradation of the reporter mRNA. The observed mRNA degradation is markedly reduced when a constitutively active mutant of MAPK kinase 6 (MKK6), which selectively activates p38 MAPK, is co-expressed.

Conclusions/Significance

Taken together, we here report p38 MAPK as a regulator of IL-24 expression and determine interference with destabilization mediated by the 3′ UTR of IL-24 mRNA as mode of action. As discussed in the present work these findings have important implications for our understanding of IL-24 as a tumor suppressor protein as well as an immune modulating cytokine.     

Immunohistochemistry of IL-1β, IL-6 and TNF-α in spleens of mice treated with gold nanoparticles

Gold nanoparticles (AuNPs) possess considerable biocompatibility and therefore gaining more attention for their biomedical applications. Previous studies have shown the transient increase in pro-inflammatory cytokines expression in different organs of rats and mice exposed to AuNPs. Structural changes in the spleen of mice treated with AuNPs have also been reported. This investigation was aimed to study the immunostaining of IL-1β, IL-6 and TNF-α in mice treated with different sizes of AuNPs. The animals were divided into 7 groups of 4 animals in each group. One group received saline and served as control. Two sets of three groups were treated with 5 nm, 20 nm and 50 nm diameter AuNPs. One set was sacrificed on day 1 and the other on day 7 following the AuNPs injections. Spleens were dissected out and promptly fixed in formalin for 3 days and then processed for IL-1β, IL-6 and TNF-α immunostaining using target-specific antibodies. The immunoreactivities of IL-1β and IL-6 were increased with the increase of AuNP size. The immunostaining of IL-1β in spleen of 20 nm AuNP treated mice was subsequently decreased on day 7 whereas it persisted in 50 nm AuNP group. The increase in the immunoreactivity of IL-6 on day 1 was decreased on day 7 in the spleens of mice treated with 20 nm or 50 nm AuNPs. The immunostaining of TNF-α was found to be negative in all the treatment groups. In conclusion, the size of AuNPs plays an important role in the expression of proinflammatory cytokines in mouse spleen; small size (5 nm) AuNPs caused minimal effect, whereas larger (50 nm) AuNPs produced intense immunostaining.     

Understanding the mechanism of IL-1β secretion

The cytokine interleukin-1β (IL-1β) is a key mediator of the inflammatory response. Essential for the host-response and resistance to pathogens, it also exacerbates damage during chronic disease and acute tissue injury. It is not surprising therefore that there is a huge level of interest in how this protein is produced and exported from cells. However, the mechanism of IL-1β release has proven to be elusive. It does not follow the conventional ER-Golgi route of secretion. A literature full of disparate observations arising from numerous experimental systems, has contributed to a complicated mix of diverse proposals. Here we summarise these observations and propose that secretion of IL-1β occurs on a continuum, dependent upon stimulus strength and the extracellular IL-1β requirement.     

IL-13 antibodies influence IL-13 clearance in humans by modulating scavenger activity of IL-13Rα2

Human studies using Abs to two different, nonoverlapping epitopes of IL-13 suggested that epitope specificity can have a clinically significant impact on clearance of IL-13. We propose that Ab modulation of IL-13 interaction with IL-13Rα2 underlies this effect. Two Abs were administered to healthy subjects and mild asthmatics in separate dose-ranging studies and allergen-challenge studies. IMA-638 allows IL-13 interaction with IL-13Rα1 or IL-13Rα2 but blocks recruitment of IL-4Rα to the IL-13/IL-13Rα1 complex, whereas IMA-026 competes with IL-13 interaction with IL-13Rα1 and IL-13Rα2. We found ～10-fold higher circulating titer of captured IL-13 in subjects treated with IMA-026 compared with those administered IMA-638. To understand how this difference could be related to epitope, we asked whether either Ab affects IL-13 internalization through cell surface IL-13Rα2. Humans inducibly express cell surface IL-13Rα2 but lack the soluble form that regulates IL-13 responses in mice. Cells with high IL-13Rα2 expression rapidly and efficiently depleted extracellular IL-13, and this activity persisted in the presence of IMA-638 but not IMA-026. The potency and efficiency of this clearance pathway suggest that cell surface IL-13Rα2 acts as a scavenger for IL-13. These findings could have important implications for the design and characterization of IL-13 antagonists.     

Incubation of antigen-sensitized T lymphocytes activated with bryostatin 1 + ionomycin in IL-7 + IL-15 increases yield of cells capable of inducing regression of melanoma metastases compared to culture in IL-2

Regression of established tumors can be induced by adoptive immunotherapy (AIT) with tumor draining lymph node (DLN) lymphocytes activated with bryostatin and ionomycin (B/I). We hypothesized that B/I-activated T cells cultured in IL-7 + IL-15 might proliferate and survive in culture better than cells cultured in IL-2, and that these cells would have equal or greater anti-tumor activity in vivo. Tumor antigen-sensitized DLN lymphocytes from either wild-type or T cell receptor transgenic mice were harvested, activated with B/I, and expanded in culture with either IL-2, IL-7 + IL-15 or a regimen of alternating cytokines. Cell yields, proliferation, apoptosis, phenotypes, and in vitro responses to tumor antigen were compared for cells grown in different cytokines. These T cells were also tested for anti-tumor activity against melanoma lung metastases established by prior i.v. injection of B16 melanoma cells. IL-7 + IL-15 or alternating cytokines resulted in much faster and prolonged proliferation and much less apopotosis of B/I-activated T cells than culturing the same cells in IL-2. This resulted in approximately tenfold greater yields of viable cells. Culture in IL-7 + IL-15 yielded higher proportions of CD8+ T cells and a higher proportion of cells with a central memory phenotype. Despite this, T cells grown in IL-7 + IL-15 had higher IFN-γ release responses to tumor antigen than cells grown in IL-2. Adoptive transfer of B/I-activated T cells grown in IL-7 + IL-15 or the alternating regimen had equal or greater efficacy on a “per-cell” basis against melanoma metastases. Activation of tumor antigen-sensitized T cells with B/I and culture in IL-7 + IL-15 is a promising modification of standard regimens for production of T cells for use in adoptive immunotherapy of cancer.     

IL-1β, IL-6, and RANTES as Biomarkers of Chikungunya Severity

Background

Little is known about the immunopathogenesis of Chikungunya virus. Circulating levels of immune mediators and growth factors were analyzed from patients infected during the first Singaporean Chikungunya fever outbreak in early 2008 to establish biomarkers associated with infection and/or disease severity.

Methods and Findings

Adult patients with laboratory-confirmed Chikungunya fever infection, who were referred to the Communicable Disease Centre/Tan Tock Seng Hospital during the period from January to February 2008, were included in this retrospective study. Plasma fractions were analyzed using a multiplex-microbead immunoassay. Among the patients, the most common clinical features were fever (100%), arthralgia (90%), rash (50%) and conjunctivitis (40%). Profiles of 30 cytokines, chemokines, and growth factors were able to discriminate the clinical forms of Chikungunya from healthy controls, with patients classified as non-severe and severe disease. Levels of 8 plasma cytokines and 4 growth factors were significantly elevated. Statistical analysis showed that an increase in IL-1β, IL-6 and a decrease in RANTES were associated with disease severity.

Conclusions

This is the first comprehensive report on the production of cytokines, chemokines, and growth factors during acute Chikungunya virus infection. Using these biomarkers, we were able to distinguish between mild disease and more severe forms of Chikungunya fever, thus enabling the identification of patients with poor prognosis and monitoring of the disease.     

Th2-inducing cytokines IL-4 and IL-33 synergistically elicit the expression of transmembrane TNF-α on macrophages through the autocrine action of IL-6

Tumor necrosis factor-α (TNF-α) is a potent proinflammatory cytokine produced predominantly by activated macrophages, and plays a central role in the protective immunity against intracellular pathogens and the pathogenesis of autoimmune and inflammatory diseases. While both the soluble and transmembrane forms of TNF-α (sTNF-α and tmTNF-α) are biologically functional, the latter but not the former acts as a receptor besides as a ligand, and transmit a retrograde signal in a cell-to-cell contact manner. The production of TNF-α by macrophages under Th2-type (allergic) inflammatory conditions has been ill defined, compared to that under Th1-type inflammatory conditions. Here we examined the effect of representative Th2-inducing cytokines IL-4 and IL-33 on the TNF-α expression in macrophages. IL-4 induced the production of neither sTNF-α nor tmTNF-α while IL-33 promoted the production of sTNF-α with no detectable tmTNF-α. Notably, the combination of IL-4 and IL-33 elicited the tmTNF-α expression on macrophages, in addition to the enhanced production of sTNF-α and IL-6. The IL-4/IL-33-elicited tmTNF-α expression was not observed in IL-6-deficient macrophages, suggesting the involvement of macrophage-derived IL-6 in the tmTNF-α expression. Indeed, the stimulation of macrophages with the combination of IL-4 and IL-6 induced the tmTNF-α expression with no detectable production of sTNF-α. Thus, IL-4 and IL-33 synergistically elicit the tmTNF-α expression on macrophages through the autocrine action of IL-6.     

Effect of short-term interferon-β treatment on cytokines in multiple sclerosis: significant modulation of IL-17 and IL-23

Therapeutic effect of interferon-β (IFN-β) treatment has been associated with modulation of the balance between Th1, Th17, Th2 and regulatory T (Treg) cells, whereas the impact of disease modifying drugs on Th9-immunity in multiple sclerosis (MS) has not been studied. To investigate the short-term effects of IFN-β treatment on cytokines in MS, we determined serum levels of IL-17, IL-23, IL-10, IL-4, IFN-γ, IL-9 and TGF-β in relapsing remitting MS patients before and 2 months after IFN-β treatment by ELISA. MS patients showed increased IL-17, IL-23 and IL-4 levels and decreased IL-9 levels as compared to healthy controls. IFN-β treatment only reduced IL-17 and IL-23 levels, whereas the levels of other cytokines remained unchanged. IFN-β treatment appears to exert its earliest therapeutic effect on Th17-immunity. The influence of IL-9 on MS pathogenesis needs to be further studied.     

Influence of Gangliosides on the IL-2– and IL-4–Dependent Cell Proliferation

Ganglioside-induced apoptosis in the cells of IL-2–dependent cytotoxic murine cell line CTLL-2 was shown to be caspase dependent: GM1-, GM2-, and GD3-induced suppression of cell proliferation was cancelled by a general caspase inhibitor Z-VAD-FMK. Ganglioside-induced apoptosis pathways are different for different individual glycolipids; the differences exist both at the initiation and effector stages of the caspase cascade. Only for GM1-induced process, molecular mechanisms of signal transduction coincide with the ones for CD95 and TNF: the participation of both the main initiation caspases 8, 1, and 4, and caspases 3 and 9 as well, has been shown. Caspase 3 participates in the pathway induced by GM3, GD1a, GD1b, and GT1b, but not by GM2. As morphological features show, tumor-associated ganglioside GM2 is also a stimulus of programmed cell death (PCD) for CTLL-2 cell line: addition of GM2 into cell culture has resulted in appearance of annexin V-positive cells and in accumulation of DNA breaks (shown by the TUNEL direct dyeing of the open ends). But a caspase 3 inhibitor Z-DEVD-FMK did not restore the cell proliferation suppressed by GM2, and addition of a fluorescent substrate of caspase 3 Ac-DEVD-AFC did not result in the fluorescence development. So caspase 3 does not participate in downstream pathways of GM2-induced cell apoptosis, and a PCD-effector system other than the apoptosome-mediated one is involved here.     

Identification of IL-18 and Th17 cells in salivary glands of patients with Sjögren's syndrome, and amplification of IL-17-mediated secretion of inflammatory cytokines from salivary gland cells by IL-18

IL-18 is a proinflammatory cytokine and plays an important pathogenic role in inflammatory and autoimmune disorders. IL-17 is also a proinflammatory cytokine and IL-17-secreting Th17 cells are involved in autoimmunity. However, the pathological roles of IL-18 and Th17 cells in Sj?gren's syndrome (SS) remain to be elucidated. This study showed that the expression of IL-18 was detected in acinar cells, intraducts, and CD68(+) macrophages in salivary glands of SS patients, but not in those of healthy subjects or patients with chronic graft-vs-host disease, by immunohistochemistry, and immunoblot analysis revealed that 24-kDa precursor form of IL-18 (proIL-18) and 18-kDa mature IL-18 were detected in SS salivary glands. The majority of the infiltrating cells in the salivary glands of SS patients were CD4(+) T cells, and CD8(+) T cells were infiltrated to a lesser extent. The predominant expression of IL-17 was found in infiltrating CD4(+) T cells, whereas a small number of infiltrating CD8(+) T cells expressed IL-17. Human salivary gland HSY and acinar AZA3 cells constitutively expressed proIL-18 and caspase-1, and a calcium ionophore A23187 induced the secretion of IL-18 from the cells. HSY and AZA3 cells expressed IL-18R and IL-17R on the cell surface, and IL-18 amplified the secretion of IL-6 and IL-8 that were induced by low amounts of IL-17. Primary salivary gland cells from normal subjects partially confirmed these findings. These results suggest that IL-18 and Th17 cells detected in the salivary glands in SS patients are associated with the pathogenesis of SS in the salivary glands.     

Different dynamics of IL-15R activation following IL-15 cis- or trans-presentation

Interleukin (IL)-15 is a cytokine critical for the homeostasis and the function of NK cells, NK-T cells, and memory CD8+ T cells. IL-15 signals are delivered through the IL-15Rβ and the common γ (γ(c)) receptor chains. The third receptor chain, IL-15Rα, confers specificity and high affinity for the cytokine. While IL-15 can activate with high affinity the trimeric receptor expressed by a target cell (cis-presentation), IL-15Rα is also known to trans-present IL-15 with high affinity to target cells expressing the IL-15Rβ/γ(c) complex. In order to compare the IL-15 cis- and trans-presentation processes, and using a T cell line expressing both IL-15Rα/β/γ(c) and IL-15Rβ/γ(c), we analyzed cell surface receptor chain down-modulation, cytokine internalization and signaling responses induced either with IL-15 (cis-presentation) or with RLI, a protein resulting from fusion between IL-15 and an extended IL-15Rα sushi domain, that mimics trans-presentation. Whereas IL-15 bound with high affinity to IL-15Rα/β/γ(c), RLI bound with a similar high affinity to IL-15Rβ/γ(c). The kinetics of cell surface IL-15R down-modulation were slower following RLI treatment than after IL-15 treatment, as were the kinetics of RLI internalization, which was slower than that of IL-15. IL-15 and RLI dose-dependently induced the activation of similar signaling pathways. However, the kinetics and duration of these activations were markedly different, RLI-induced signaling, being slower, but more prolonged than that induced by IL-15, although the final proliferative responses at 48?h were similar. These findings collectively indicate that IL-15 cis- and trans-presentation mechanisms lead to different dynamics of receptor activation and signal transduction, with cis-presentation inducing fast and transient responses, and trans-presentation inducing slower, more persistent ones. They provide clues for a better understanding of how IL-15 action is controlled, and how it plays a key role in the coordination between innate and adaptative immunity.     

A new regulation of IL-6 production in adult cardiomyocytes by β-adrenergic and IL-1β receptors and induction of cellular hypertrophy by IL-6 trans-signalling

The sympathetic nervous system and pro-inflammatory cytokines play key roles in numerous cardiovascular disorders. Chronic β-adrenergic receptor (β-AR) stimulation in myocardium induces expression of pro-inflammatory cytokines, such as interleukin-1 (IL-1) and interleukin-6 (IL-6), which contribute to cardiac hypertrophy and failure. To evaluate the relationship between β-AR stimulation and pro-inflammatory cytokines, we studied the effects of the β-AR agonist isoprenaline (ISO) on IL-1-induced IL-6 production in adult rat ventricular myocytes (ARVMs). We report that ISO and IL-1 synergistically enhanced IL-6 gene expression and secretion. The synergistic effect of ISO was mimicked by cAMP elevating agents and involved the G_s protein/cAMP/PKA signalling pathway, but not the exchange factor EPAC. To evaluate the contribution of IL-6 to cellular hypertrophy, we examined the signalling pathways stimulated by the membrane-bound IL-6 receptor (IL-6R), and the IL-6 soluble receptor (sIL-6R) involved in the mechanism named IL-6 trans-signalling. The IL-6/sIL-6R complex promoted a rapid and persistent phosphorylation of STAT3^Tyr705 in ARVMs. Moreover, IL-6 trans-signalling increased protein synthesis, c-fos gene expression and B-type natriuretic peptide secretion, three markers of cardiac hypertrophy. IL-6 trans-signalling also increased cell size. In contrast, IL-6 alone had no significant effect on either cell size or STAT3 phosphorylation although it induced phosphorylation of ERK1/2, AKT and S6K, demonstrating the presence of a functional IL-6R in ARVMs. Taken together, these results demonstrate that β-AR stimulation synergises with IL-1 for IL-6 secretion in adult ventricular myocytes and indicate that IL-6 induces cardiac hypertrophy only via IL-6 trans-signalling. The IL-6 soluble receptor may thus serve as a switch for IL-6 to activate STAT3 phosphorylation and hypertrophy.     

Atherogenic effects of TNF-α and IL-6 via up-regulation of scavenger receptors

Patients with chronic inflammatory disorders such as rheumatoid arthritis (RA) have a high risk of developing cardiovascular disease. We evaluated the effects of TNF-α and IL-6 on foam cell formation, a pivotal process in atherogenesis. Accumulation of intracellular oxidized LDL (oxLDL) was induced when THP-1/macrophages were stimulated with TNF-α or IL-6. TNF-α induced the expressions of scavenger receptors SR-A and LOX-1, and IL-6 induced SR-A expression. Inhibition of the NF-κB signaling markedly decreased TNF-α-induced foam cell formation and SR-A expression. Serum from RA patients, but not healthy subjects, induced foam cell formation, which was partially reversed by either IL-6 or TNF-α blockade in conjunction with inhibiting the induction of scavenger receptors. The present study clearly showed that in patients with chronic inflammation mediated by TNF-α and IL-6, these cytokines are directly implicated in atherosclerotic plaque formation.     

Brain IL-6- and PG-dependent actions of IL-1β and lipopolysaccharide in avian fever

There is no persuasive evidence of a correlation between proinflammatory cytokines and avian fever. In this study, for the first time, we use avian cytokines to investigate a role for proinflammatory cytokines in the central component of avian fever. IL-1β and IL-6 injected intracerebroventricularly into Pekin ducks (n = 8) initiated robust fevers of equal magnitude and duration, although there was a significant difference in the latency to a febrile response. In addition, the IL-1β-induced fever could be abolished with an intracerebroventricular injection of antibodies to avian IL-6 or an oral administration of a PG synthesis inhibitor. Our findings indicate the following sequence of events within the central component of the avian febrile mechanism: IL-1β gives rise to bioactive IL-6, which stimulates an accelerated synthesis of PGs, and these PGs then adjust the sensitivity of warm-sensitive neurons in the avian brain stem to mediate fever. Yet PGE? was not upregulated in the cerebrospinal fluid of ducks made febrile with LPS. We conclude that IL-1β and IL-6 may well mediate fever by instigating an accelerated synthesis of brain-derived PG, of a class other than PGE?, or that IL-6 serves as one of the terminal mediators of the avian febrile response.