The IL-36 receptor pathway regulates Aspergillus fumigatus-induced Th1 and Th17 responses

The enigmatic role of IL-38 in inflammatory diseases

IL-38 is the most recently discovered cytokine of the IL-1 family and is considered a potential inhibitor of the IL-1 and Toll-like receptor families. IL-38 exerts anti-inflammatory properties, especially on macrophages, by inhibiting secretion of pro-inflammatory cytokines, leading to reduced T-lymphocyte TH17 maturation. IL-38 has been studied most extensively in the context of chronic inflammatory diseases, particularly arthritis, where it is considered an attractive new drug candidate. IL-38 research has entered a new phase, with the realization that IL-38 is important in the pathophysiology of TH17 dependent-diseases (psoriasis, psoriatic arthritis and ankylosing spondylitis). In this review, we provide a critical evaluation of several controversial issues concerning IL-38 function and regulation. There is effectively contrasting data regarding IL-38: it is produced in conditions such as apoptosis, necrosis or inflammation, but data is lacking regarding IL-38 processing and biological function. Furthermore, the receptor for IL-38 has yet to be identified, although three candidate receptors - IL-1R1, IL-36R and IL-1RAPL1-have been proposed. Future studies will hopefully uncover new aspects of this enigmatic cytokine.

Elevated Interleukin-36α And CD4+IL-36α+T Cells Are Involved in the Pathogenesis of Graves' Disease

Background: IL-36α is involved in the pathogenesis of a variety of autoimmune diseases, but the relationship between IL-36α and Graves' disease (GD) has rarely investigated. In the present study, we aimed to explore the expression of IL-36α and elucidate the potential role of IL-36α in GD. Methods: The expression of IL-36α mRNA in peripheral blood mononuclear cells (PBMCs) from 32 newly diagnosed GD patients, 15 refractory GD patients and 30 normal controls (NC) was examined using quantitative real-time polymerase chain reaction (qRT-PCR). The level of IL-36α in serum from 46 newly diagnosed GD patients, 10 refractory GD patients and 24 NC was measured using enzyme linked immunosorbent assay (ELISA). The percentage of CD4⁺IL-36α⁺T cells was detected by flow cytometry. PBMCs from newly diagnosed GD patients and NC group were cultured in the presence or absence of recombinant human IL-36α, and the expression levels of IFN-γ, TNF-α, IL-6, and IL-17A in culture supernatant were detected by cytokine array. Results: The expression of IL-36α mRNA in newly diagnosed GD patients was significantly higher than that in NC group (P = 0.019). IL-36α mRNA expression was positively associated with thyrotropin receptor antibody (TRAb) (P = 0.004, r = 0.498) in newly diagnosed GD patients. The level of IL-36α in serum from newly diagnosed GD patients was significantly higher than that in refractory GD patients and NC group (P = 0.01; P = 0.007). The percentage of CD4⁺IL-36α⁺T cells in newly diagnosed GD patients was significantly higher than that in NC group (P = 0.030). In GD group, recombinant human IL-36α stimulation resulted in the increase of INF-γ, TNF-α, IL-6 and IL-17A (P = 0.015; P = 0.016; P = 0.039; P = 0.017). Conclusion: IL-36α and CD4⁺IL-36α⁺T cells may be involved in the pathogenesis of GD by promoting the production of Th1, Th2, and Th17 cytokines.

The Multifaceted Role of T-Helper Responses in Host Defense against Aspergillus fumigatus

The ubiquitous opportunistic fungal pathogen Aspergillus fumigatus rarely causes infections in immunocompetent individuals. A healthy functional innate immune system plays a crucial role in preventing Aspergillus-infection. This pivotal role for the innate immune system makes it a main research focus in studying the pathogenesis of aspergillosis. Although sometimes overshadowed by the innate immune response, the adaptive immune response, and in particular T-helper responses, also represents a key player in host defense against Aspergillus. Virtually all T-helper subsets have been described to play a role during aspergillosis, with the Th1 response being crucial for fungal clearance. However; morbidity and mortality of aspergillosis can also be partly attributed to detrimental immune responses resulting from adaptive immune activation. Th2 responses benefit fungal persistence; and are the foundation of allergic forms of aspergillosis. The Th17 response has two sides; although crucial for granulocyte recruitment, it can be involved in detrimental immunopathology. Regulatory T-cells, the endogenous regulators of inflammatory responses, play a key role in controlling detrimental inflammatory responses during aspergillosis. The current knowledge of the adaptive immune response against A. fumigatus is summarized in this review. A better understanding on how T-helper responses facilitate clearance of Aspergillus-infection and control inflammation can be the fundamental basis for understanding the pathogenesis of aspergillosis and for the development of novel host-directed therapies.

IL-33 Signaling Regulates Innate IL-17A and IL-22 Production via Suppression of Prostaglandin E2 during Lung Fungal Infection

Members of the IL-1 family play protective and regulatory roles in immune defense against the opportunistic mold Aspergillus fumigatus In this study, we investigated the IL-1 family member IL-33 in lung defense against A. fumigatus IL-33 was detected in the naive lung, which further increased after exposure to A. fumigatus in a dectin-1-independent manner. Mice deficient in the receptor for IL-33 (Il1rl1-/-) unexpectedly demonstrated enhanced lung clearance of A. fumigatus IL-33 functioned as a negative regulator of multiple inflammatory cytokines, as IL-1α, IL-1β, IL-6, IL-17A, and IL-22 were significantly elevated in fungal-exposed Il1rl1-/- mice. Subsequently, IL-33 administration to normal mice attenuated fungal-induced IL-17A and IL-22, but not IL-1α, IL-1β, or IL-6, production. IL-33-mediated regulation of IL-17A and IL-22 did not involve the modulation of IL-23 but rather PGE2; PGE2 was significantly increased in fungal-exposed Il1rl1-/- mice, and normal mice produced less PGE2 after fungal exposure when administered IL-33, suggesting that IL-33-mediated regulation of IL-17A and IL-22 occurred at the level of PGE2 This was confirmed by in vivo cyclooxygenase 2 inhibition, which attenuated fungal-induced IL-17A and IL-22, as well as IL-1α, IL-1β, and IL-6, production in Il1rl1-/- mice, resulting in impaired fungal clearance. We also show that a PGE2 receptor agonist increased, whereas a PGE2 synthase inhibitor decreased, the levels of IL-17A and IL-22 but not IL-1α, IL-1β, or IL-6. This study establishes novel mechanisms of innate IL-17A/IL-22 production via PGE2 and regulation of the PGE2/IL-17A/IL-22 axis via IL-33 signaling during lung fungal exposure.

Levels of interleukin (IL)-6 and IL-8 are elevated in serum and bronchoalveolar lavage fluid of haematological patients with invasive pulmonary aspergillosis

Aspergillus spp. have been shown to induce T-helper cell (Th) 1 and Th17 subsets resulting in elevated levels of several cytokines. The objective of this study was to analyse a bundle of cytokines in serum and bronchoalveolar lavage fluid (BALF) in patients with and without invasive pulmonary aspergillosis (IPA). This nested case-control analysis included 10 patients with probable/proven IPA and 20 matched controls without evidence of IPA, out of a pool of prospectively enrolled (2014-2017) adult cases with underlying haematological malignancies and suspected pulmonary infection. Serum samples were collected within 24 hours of BALF sampling. All samples were stored at -70°C for retrospective determination of cytokines. IL-6 and IL-8 were significantly associated with IPA in both serum (P = .011 and P = .028) and BALF (P = .006 and P = .012, respectively), and a trend was observed for serum IL-10 (P = .059). In multivariate conditional logistic regression analysis, IL-10 remained a significant predictor of IPA in serum and IL-8 among BALF cytokines. In conclusion, levels of IL-6 and IL-8 were significantly associated with probable/proven IPA, and a similar trend was observed for serum IL-10. Future cohort studies should determine the diagnostic potential of these cytokines for IPA, and evaluate combinations with other IPA biomarkers/diagnostic tests.

IL-36 induces cytokine IL-6 and chemokine CXCL8 expression in human lung tissue cells: Implications for pulmonary inflammatory responses

IL-36α, IL-36β and IL-36γ are cytokine members of IL-1 family. Although IL-36 expression was observed in human lung during pulmonary infections, it remains unknown whether IL-36 could act directly on lung tissue cells during pulmonary inflammatory responses. In this study, we showed that IL-36 receptor was expressed in human lung fibroblasts and bronchial epithelial cells. Correspondingly, IL-36α, IL-36β or IL-36γ up-regulated gene expression of cytokine IL-6 and chemokine CXCL8 in human lung fibroblasts and bronchial epithelial cells, and promoted IL-6 and CXCL8 release from human lung fibroblasts and bronchial epithelial cells. The production of IL-6 and CXCL8 in these lung tissues cells induced by IL-36α, IL-36β or IL-36γ was regulated by p38MAPK, ERK or Akt signaling pathways. Taken together, the above results suggest that IL-36-mediated IL-6 and CXCL8 production in human lung fibroblasts and bronchial epithelial cells may be involved in pulmonary inflammation especially caused by bacterial or viral infections.

IL-36γ is a crucial proximal component of protective type-1-mediated lung mucosal immunity in Gram-positive and -negative bacterial pneumonia

Interleukin-36γ (IL-36γ) is a member of novel IL-1-like proinflammatory cytokine family that are highly expressed in epithelial tissues and several myeloid-derived cell types. Little is known about the role of the IL-36 family in mucosal immunity, including lung anti-bacterial responses. We used murine models of IL-36γ deficiency to assess the contribution of IL-36γ in the lung during experimental pneumonia. Induction of IL-36γ was observed in the lung in response to Streptococcus pneumoniae (Sp) infection, and mature IL-36γ protein was secreted primarily in microparticles. IL-36γ-deficient mice challenged with Sp demonstrated increased mortality, decreased lung bacterial clearance and increased bacterial dissemination, in association with reduced local expression of type-1 cytokines, and impaired lung macrophage M1 polarization. IL-36γ directly stimulated type-1 cytokine induction from dendritic cells in vitro in a MyD88-dependent manner. Similar protective effects of IL-36γ were observed in a Gram-negative pneumonia model (Klebsiella pneumoniae). Intrapulmonary delivery of IL-36γ-containing microparticles reconstituted immunity in IL-36γ^-/- mice. Enhanced expression of IL-36γ was also observed in plasma and bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome because of pneumonia. These studies indicate that IL-36γ assumes a vital proximal role in the lung innate mucosal immunity during bacterial pneumonia by driving protective type-1 responses and classical macrophage activation.

Innate Lung Defense during Invasive Aspergillosis: New Mechanisms

Invasive aspergillosis (IA) is one of the most difficult to treat and, consequently, one of the most lethal fungal infections known to man. Continued use of immunosuppressive agents during chemotherapy and organ transplantation often leads to the development of neutropenia, the primary risk factor for IA. However, IA is also becoming more appreciated in chronic diseases associated with corticosteroid therapy. The innate immune response to Aspergillus fumigatus, the primary agent in IA, plays a pivotal role in the recognition and elimination of organisms from the pulmonary system. This review highlights recent findings about innate host defense mechanisms, including novel aspects of innate cellular immunity and pathogen recognition, and the inflammatory mediators that control infection with A. fumigatus.

The emergence of the IL-36 cytokine family as novel targets for inflammatory diseases

The recently discovered interleukin (IL)-36 family of cytokines form part of the broader IL-1 family and are emerging as important mediators of inflammatory disease. The IL-36 subfamily consists of three ligands-IL-36α, IL-36β, and IL-36γ-and the natural antagonist IL-36Ra. The cytokines exert their effects through a specific IL-36 receptor consisting of IL-36R and IL-1RAcP chains. IL-36 cytokines can direct both innate and adaptive immune responses by acting on parenchymal, stromal, and specific immune cell subsets. In humans, inactivating mutations in the gene encoding the IL-36R antagonist, which lead to unregulated IL-36R signaling, lead to an autoinflammatory condition termed deficiency of the IL-36R antagonist, which primarily manifests as a severe form of pustular psoriasis. While such discoveries have prompted deeper mechanistic studies highlighting the important role of IL-36 cytokines in psoriatic skin inflammation, it is now evident that IL-36 cytokines can also play important roles in inflammatory disorders in other organs, such as the gastrointestinal tract and the lungs. Given these emerging roles, strategies to specifically target the expression and activity of the IL-36 family have the potential to uncover novel therapeutic approaches aimed at treating inflammatory diseases in humans.

IL-36α expression is elevated in ulcerative colitis and promotes colonic inflammation

A role for the IL-36 family of cytokines has been identified in the pathogenesis of psoriasis. Although significant mechanistic overlap can exist between psoriasis and inflammatory bowel disease (IBD), to date there have been no reports investigating the IL-36 family in gastrointestinal inflammation. Here we demonstrate that expression levels of IL-36α are specifically elevated in the colonic mucosa of ulcerative colitis patients. This elevated expression is mirrored in the inflamed colonic mucosa of mice, wherein IL-36 receptor deficiency confirmed this pathway as a mediator of mucosal inflammation. Il36r-/- mice exhibited reduced disease severity in an acute DSS-induced model of colitis in association with decreased innate inflammatory cell infiltration to the colon lamina propria. Consistent with these data, infection with the enteropathogenic bacteria Citrobacter rodentium, resulted in reduced innate inflammatory cell recruitment and increased bacterial colonization in the colons of il36r-/- mice. Il36r-/- mice also exhibited altered T helper cell responses in this model, with enhanced Th17 and reduced Th1 responses, demonstrating that IL-36R signaling also regulates intestinal mucosal T-cell responses. These data identify a novel role for IL-36 signaling in colonic inflammation and indicate that the IL-36R pathway may represent a novel target for therapeutic intervention in IBD.

IL-36γ Augments Host Defense and Immune Responses in Human Female Reproductive Tract Epithelial Cells

IL-36γ is a proinflamatory cytokine which belongs to the IL-1 family of cytokines. It is expressed in the skin and by epithelial cells (ECs) lining lung and gut tissue. We used human 3-D organotypic cells, that recapitulate either in vivo human vaginal or cervical tissue, to explore the possible role of IL-36γ in host defense against pathogens in the human female reproductive tract (FRT). EC were exposed to compounds derived from virus or bacterial sources and induction and regulation of IL-36γ and its receptor was determined. Polyinosinic-polycytidylic acid (poly I:C), flagellin, and synthetic lipoprotein (FSL-1) significantly induced expression of IL-36γ in a dose-dependent manner, and appeared to be TLR-dependent. Recombinant IL-36γ treatment resulted in self-amplification of IL-36γ and its receptor (IL-36R) via increased gene expression, and promoted other inflammatory signaling pathways. This is the first report to demonstrate that the IL-36 receptor and IL-36γ are present in the human FRT EC and that they are differentially induced by microbial products at this site. We conclude that IL-36γ is a driver for epithelial and immune activation following microbial insult and, as such, may play a critical role in host defense in the FRT.

Neutrophil Elastase-mediated proteolysis activates the anti-inflammatory cytokine IL-36 Receptor antagonist

The interleukin-36 receptor antagonist (IL-36Ra) which regulates IL-36α, -β and -γ is linked to psoriatic inflammation, especially loss-of-function mutations in pustular psoriasis subtypes. As observed with other IL-1 superfamily proteins, the IL-36 members require N-terminal cleavage for full biological activity but the mechanisms of IL-36Ra activation remain poorly defined. Using different blood leukocyte and skin resident cell preparations, and recombinant proteins, we have identified that neutrophil elastase, but not other neutrophil derived proteases, cleaves IL-36Ra into its highly active antagonistic form. The activity of this processed form of IL-36Ra was confirmed in human primary dermal fibroblasts and keratinocytes and in skin equivalents. A significant dose dependent reduction of IL-36γ induced IL-8 and chemokine ligand 20 (CCL20) levels were detected following addition of the cleaved IL-36Ra compared to full length IL-36Ra. By activating IL-36Ra, the neutrophil derived protease can inhibit IL-36 induced chemokine production, including IL-8 and CCL20, and reduce further inflammatory cell infiltration. These findings strongly indicate neutrophil elastase to be a key enzyme in the biological function of IL-36Ra and that neutrophils can play a regulatory role in psoriatic inflammation with regard to balancing the pro-inflammatory activity of IL-36.

Distinct expression of interleukin (IL)-36α, β and γ, their antagonist IL-36Ra and IL-38 in psoriasis, rheumatoid arthritis and Crohn's disease

Interleukin (IL)-36α, IL-36β and IL-36γ are expressed highly in skin and are involved in the pathogenesis of psoriasis, while the antagonists IL-36Ra or IL-38, another potential IL-36 inhibitor, limit uncontrolled inflammation. The expression and role of IL-36 cytokines in rheumatoid arthritis (RA) and Crohn's disease (CD) is currently debated. Here, we observed that during imiquimod-induced mouse skin inflammation and in human psoriasis, expression of IL-36α, γ and IL-36Ra, but not IL-36β and IL-38 mRNA, was induced and correlated with IL-1β and T helper type 17 (Th17) cytokines (IL-17A, IL-22, IL-23, CCL20). In mice with collagen-induced arthritis and in the synovium of patients with RA, IL-36α, β, γ, IL-36Ra and IL-38 were all elevated and correlated with IL-1β, CCL3, CCL4 and macrophage colony-stimulating factor (M-CSF), but not with Th17 cytokines. In the colon of mice with dextran sulphate sodium-induced colitis and in patients with CD, only IL-36α, γ and IL-38 were induced at relatively low levels and correlated with IL-1β and IL-17A. We suggest that only a minor subgroup of patients with RA (17-29%) or CD (25%) had an elevated IL-36 agonists/antagonists ratio, versus 93% of patients with psoriasis. By immunohistochemistry, IL-36 cytokines were produced by various cell types in skin, synovium and colonic mucosa such as keratinocytes, CD68⁺ macrophages, dendritic/Langerhans cells and CD79α⁺ plasma cells. In primary cultures of monocytes or inflammatory macrophages (M1), IL-36β and IL-36Ra were produced constitutively, but IL-36α, γ and IL-38 were produced after lipopolysaccharide stimulation. These distinct expression profiles may help to explain why only subgroups of RA and CD patients have a potentially elevated IL-36 agonists/antagonists ratio.

IL-36γ is secreted in microparticles and exosomes by lung macrophages in response to bacteria and bacterial components

Interleukin-36 is a family of novel interleukin-1-like proinflammatory cytokines that are highly expressed in epithelial tissues and several myeloid-derived cell types. Like those of classic interleukin-1 cytokines, the secretion mechanisms of interleukin-36 are not well understood. Interleukin-36γ secretion in dermal epithelial cells requires adenosine 5'-triphosphate, which suggests a nonclassical mechanism of secretion. In this study, murine pulmonary macrophages and human alveolar macrophages were treated with recombinant pathogen-associated molecular patterns (intact bacteria: Klebsiella pneumoniae or Streptococcus pneumoniae). Cell lysates were analyzed for messenger ribonucleic acid by quantitative real-time polymerase chain reaction, and conditioned medium was analyzed for interleukin-36γ by enzyme-linked immunosorbent assay, with or without sonication. In addition, conditioned medium was ultracentrifuged at 25,000 g and 100,000 g, to isolate microparticles and exosomes, respectively, and interleukin-36γ protein was assessed in each fraction by Western blot analysis. Interleukin-36γ mRNA was induced in both murine and human lung macrophages by a variety of pathogen-associated molecular patterns, as well as heat-killed and live Klebsiella pneumoniae and Streptococcus pneumoniae, and induction occurred in a myeloid differentiation response gene 88-dependent manner. Secretion of interleukin-36γ protein was enhanced by adenosine 5'-triphosphate. Furthermore, extracellular interleukin-36γ protein detection was markedly enhanced by sonication to disrupt membrane-bound structures. Interleukin-36γ protein was detected by Western blot in microparticles and exosome fractions isolated by ultracentrifugation. Interleukin-36γ was induced and secreted from lung macrophages in response to Gram-negative and -positive bacterial stimulation. The results suggest that interleukin-36γ is secreted in a non-Golgi-dependent manner by lung macrophages in response to Gram-positive and -negative bacterial challenge.

Increased Expression of Interleukin-36, a Member of the Interleukin-1 Cytokine Family, in Inflammatory Bowel Disease

BACKGROUND

Interleukin (IL)-36 (IL-36α, IL-36β, and IL-36γ) is a recently reported member of the IL-1 cytokine family. In this study, we investigated IL-36 expression in the inflamed mucosa of patients with inflammatory bowel disease and characterized the proinflammatory actions of IL-36 cytokines in human colonic epithelial cells.

METHODS

IL-36 mRNA expression was evaluated using real-time PCR. IL-36 protein expression was analyzed using immunoblotting and immunohistochemical technique. Intracellular signaling pathways were evaluated by immunoblotting and by specific siRNA-transfected cells.

RESULTS

The mRNA expression of IL-36α and IL-36γ, but not of IL-36β, was enhanced in the inflamed mucosa of patients with inflammatory bowel disease, in particular, in ulcerative colitis. Immunohistochemical analysis showed that T cells, monocytes, and plasma cells are the source of IL-36α and IL-36γ in colonic mucosa. DNA microarray analysis indicated that IL-36α induces the mRNA expression of CXC chemokines and acute phase proteins in intestinal epithelial cell line, HT-29 cells. IL-36α and IL-36γ dose-dependently and time-dependently induced the mRNA and protein expression of CXC chemokines (CXCL1, CXCL2, CXCL3 etc.) in HT-29 and Widr cells. Stimulation with IL-36α and IL-36γ assembled MyD88 adaptor proteins (MyD88, TRAF6, IRAK1, and TAK1) into a complex and induced the activation of NF-κB and AP-1 and also the phosphorylation of MAPKs. MAPK inhibitors and siRNAs specific for NF-κB and c-Jun AP-1 significantly reduced IL-36-induced CXC chemokine expression.

CONCLUSIONS

IL-36α and IL-36γ may play a proinflammatory role in the pathophysiology of inflammatory bowel disease through induction of CXC chemokines and acute phase proteins.

Optimizing Outcomes in Immunocompromised Hosts: Understanding the Role of Immunotherapy in Invasive Fungal Diseases

A major global concern is the emergence and spread of systemic life-threatening fungal infections in critically ill patients. The increase in invasive fungal infections, caused most commonly by Candida and Aspergillus species, occurs in patients with impaired defenses due to a number of reasons such as underlying disease, the use of chemotherapeutic and immunosuppressive agents, broad-spectrum antibiotics, prosthetic devices and grafts, burns, neutropenia and HIV infection. The high morbidity and mortality associated with these infections is compounded by the limited therapeutic options and the emergence of drug resistant fungi. Hence, creative approaches to bridge the significant gap in antifungal drug development needs to be explored. Here, we review the potential anti-fungal targets for patient-centered therapies and immune-enhancing strategies for the prevention and treatment of invasive fungal diseases.

Costimulation Endows Immunotherapeutic CD8 T Cells with IL-36 Responsiveness during Aerobic Glycolysis

CD134- and CD137-primed CD8 T cells mount powerful effector responses upon recall, but even without recall these dual-costimulated T cells respond to signal 3 cytokines such as IL-12. We searched for alternative signal 3 receptor pathways and found the IL-1 family member IL-36R. Although IL-36 alone did not stimulate effector CD8 T cells, in combination with IL-12, or more surprisingly IL-2, it induced striking and rapid TCR-independent IFN-γ synthesis. To understand how signal 3 responses functioned in dual-costimulated T cells we showed that IL-2 induced IL-36R gene expression in a JAK/STAT-dependent manner. These data help delineate a sequential stimulation process where IL-2 conditioning must precede IL-36 for IFN-γ synthesis. Importantly, this responsive state was transient and functioned only in effector T cells capable of aerobic glycolysis. Specifically, as the effector T cells metabolized glucose and consumed O2, they also retained potential to respond through IL-36R. This suggests that T cells use innate receptor pathways such as the IL-36R/axis when programmed for aerobic glycolysis. To explore a function for IL-36R in vivo, we showed that dual costimulation therapy reduced B16 melanoma tumor growth while increasing IL-36R gene expression. In summary, cytokine therapy to eliminate tumors may target effector T cells, even outside of TCR specificity, as long as the effectors are in the correct metabolic state.

Interleukin (IL)-1β Is a Strong Inducer of IL-36γ Expression in Human Colonic Myofibroblasts

BACKGROUNDS AND AIMS

Interleukin (IL)-36 cytokines are members of the IL-1 cytokine family. In this study, we investigated the expression of IL-36γ in human colonic myofibroblasts to explore the molecular mechanisms underlying IL-36γ induction.

MATERIALS AND METHODS

IL-36 mRNA was analyzed by real-time PCR method. Secretion of IL-36γ protein was evaluated by Western blot and ELISA analyses. Molecular mechanism of IL-36γ induction was evaluated by siRNA analyses and immunofluorescence experiments.

RESULTS

IL-36γ mRNA expression was scarcely detected in the cells without stimulation. IL-1β induced a marked increase of IL-36γ mRNA expression. TNF-α markedly enhanced IL-1β-induced IL-36γ mRNA expression. These responses were confirmed at the protein levels. The inhibitors for ERK1/2 (PD98059 and U0216) and a p38 MAPK (SB203580) significantly reduced the IL-1β-induced IL-36γ mRNA expression. In addition, the siRNAs specific for NF-κB p65 and AP-1 (c-Jun) significantly reduced the expression of IL-1β-induced IL-36γ mRNA.

CONCLUSIONS

Colonic myofibroblasts are cellular source of IL-36γ in the intestine. IL-36γ expression was induced by the combination of IL-1β and TNF-α via activation of MAPKs and transcription factors, NF-κB and AP-1.

Interleukin(IL)-36α and IL-36γ Induce Proinflammatory Mediators from Human Colonic Subepithelial Myofibroblasts

BACKGROUND

Interleukin (IL)-36 cytokines are recently reported member of the IL-1 cytokine family. However, there is little information regarding the association between IL-36 cytokines and gut inflammation. In the present study, we investigated the biological activity of IL-36α and IL-36γ using human colonic subepithelial myofibroblasts (SEMFs).

METHODS

The mRNA expression and the protein expression of target molecules in SEMFs were evaluated using real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The intracellular signaling of IL-36 cytokines was analyzed using Western blot analysis and small interfering RNAs (siRNAs) specific for MyD88 adaptor proteins (MyD88 and IRAK1) and NF-κB p65.

RESULTS

IL-36α and IL-36γ significantly enhanced the secretion of IL-6 and CXC chemokines (CXCL1, CXCL2, and CXCL8) by SEMFs. The combination of IL-36α/γ and IL-17A or of IL-36α/γ and tumor necrosis factor-α showed a synergistic effect on the induction of IL-6 and CXC chemokines. The mRNA expression of proinflammatory mediators induced by IL-36α and/or IL-36γ was significantly suppressed by transfection of siRNA for MyD88 or IRAK1. Both inhibitors of mitogen activated protein kinases and siRNAs specific for NF-κBp65 significantly reduced the expression of IL-6 and CXC chemokines induced by IL-36α and/or IL-36γ.

CONCLUSION

These results suggest that IL-36α and IL-36γ contribute to gut inflammation through the induction of proinflammatory mediators.

Interleukin-36γ is expressed by neutrophils and can activate microglia, but has no role in experimental autoimmune encephalomyelitis

Background

Experimental autoimmune encephalomyelitis (EAE) is a model of inflammatory demyelinating diseases mediated by different types of leukocytes. How these cells communicate with each other to orchestrate autoimmune attacks is not fully understood, especially in the case of neutrophils, whose importance in EAE is newly established. The present study aimed to determine the expression pattern and role of different components of the IL-36 signaling pathway (IL-36α, IL-36β, IL-36γ, IL-36R) in EAE.

Methods

EAE was induced by either active immunization with myelin peptide, passive transfer of myelin-reactive T cells or injection of pertussis toxin to transgenic 2D2 mice. The molecules of interest were analyzed using a combination of techniques, including quantitative real-time PCR (qRT-PCR), flow cytometry, Western blotting, in situ hybridization, and immunohistochemistry. Microglial cultures were treated with recombinant IL-36γ and analyzed using DNA microarrays. Different mouse strains were subjected to clinical evaluation and flow cytometric analysis in order to compare their susceptibility to EAE.

Results

Our observations indicate that both IL-36γ and IL-36R are strongly upregulated in nervous and hematopoietic tissues in different forms of EAE. IL-36γ is specifically expressed by neutrophils, while IL-36R is expressed by different immune cells, including microglia and other myeloid cells. In culture, microglia respond to recombinant IL-36γ by expressing molecules involved in neutrophil recruitment, such as Csf3, IL-1β, and Cxcl2. However, mice deficient in either IL-36γ or IL-36R develop similar clinical and histopathological signs of EAE compared to wild-type controls.

Conclusion

This study identifies IL-36γ as a neutrophil-related cytokine that can potentially activate microglia, but that is only correlative and not contributory in EAE.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0392-7) contains supplementary material, which is available to authorized users.

IL-36γ Transforms the Tumor Microenvironment and Promotes Type 1 Lymphocyte-Mediated Antitumor Immune Responses

Cytokines play a pivotal role in regulating tumor immunogenicity and antitumor immunity. IL-36γ is important for the IL-23/IL-17-dominated inflammation and anti-BCG Th1 immune responses. However, the impact of IL-36γ on tumor immunity is unknown. Here we found that IL-36γ stimulated CD8(+) T cells, NK cells, and γδ T cells synergistically with TCR signaling and/or IL-12. Importantly, IL-36γ exerted profound antitumor effects in vivo and transformed the tumor microenvironment in favor of tumor eradication. Furthermore, IL-36γ strongly increased the efficacy of tumor vaccination. Moreover, IL-36γ expression inversely correlated with the progression of human melanoma and lung cancer. Our study establishes a role of IL-36γ in promoting antitumor immune responses and suggests its potential clinical translation into cancer immunotherapy.

Interleukin-36α axis is modulated in patients with primary Sjögren's syndrome

The aim of this study was to investigate the expression of the interleukin (IL)-36 axis in patients with primary Sjögren's syndrome (pSS). Blood and minor labial salivary glands (MSG) biopsies were obtained from 35 pSS and 20 non-Sjögren's syndrome patients (nSS) patients. Serum IL-36α was assayed by enzyme-linked immunosorbent assay (ELISA). IL-36α, IL-36R, IL-36RA, IL-38, IL-22, IL-17, IL-23p19 and expression in MSGs was assessed by reverse transcription-polymerase chain reaction (RT-PCR), and tissue IL-36α and IL-38 expression was also investigated by immunohistochemistry (IHC). αβ and γδ T cells and CD68(+) cells isolated from MSGs were also studied by flow cytometry and confocal microscopy analysis. IL-36α was over-expressed significantly in the serum and in the salivary glands of pSS. Salivary gland IL-36α expression was correlated with the expression levels of IL-17, IL-22 and IL-23p19. IL-38, that acts as inhibitor of IL-36α, was also up-regulated in pSS. αβ(+) CD3(+) T cells and CD68(+) cells were the major source of IL-36α in minor salivary glands of pSS. γδ T cells were not significantly expanded in the salivary glands of pSS but produced more IL-17, as their percentage correlated with the focus score. Higher expression of IL-36α and IL-36R was also demonstrated in γδ T cells isolated from pSS compared to controls. In this study we demonstrate that a significant increase in circulating and tissue levels of IL-36α occurs in pSS patients.

Limited Contribution of IL-36 versus IL-1 and TNF Pathways in Host Response to Mycobacterial Infection

IL-36 cytokines are members of the IL-1 family of cytokines that stimulate dendritic cells and T cells leading to enhanced T helper 1 responses in vitro and in vivo; however, their role in host defense has not been fully addressed thus far. The objective of this study was to examine the role of IL-36R signaling in the control of mycobacterial infection, using models of systemic attenuated M. bovis BCG infection and virulent aerogenic M. tuberculosis infection. IL-36γ expression was increased in the lung of M. bovis BCG infected mice. However, IL-36R deficient mice infected with M. bovis BCG showed similar survival and control of the infection as compared to wild-type mice, although their lung pathology and CXCL1 response were transiently different. While highly susceptible TNF-α deficient mice succumbed with overwhelming M. tuberculosis infection, and IL-1RI deficient mice showed intermediate susceptibility, IL-36R-deficient mice controlled the infection, with bacterial burden, lung inflammation and pathology, similar to wild-type controls. Therefore, IL-36R signaling has only limited influence in the control of mycobacterial infection.

Role of IL-38 and its related cytokines in inflammation

Interleukin- (IL-) 38 is a recently discovered cytokine and is the tenth member of the IL-1 cytokine family. IL-38 shares structural features with IL-1 receptor antagonist (IL-1Ra) and IL-36Ra. IL-36R is the specific receptor of IL-38, a partial receptor antagonist of IL-36. IL-38 inhibits the production of T-cell cytokines IL-17 and IL-22. IL-38 also inhibits the production of IL-8 induced by IL-36γ, thus inhibiting inflammatory responses. IL-38-related cytokines, including IL-1Ra and IL-36Ra, are involved in the regulation of inflammation and immune responses. The study of IL-38 and IL-38-related cytokines might provide new insights for developing anti-inflammatory treatments in the near future.

Compartment-specific and sequential role of MyD88 and CARD9 in chemokine induction and innate defense during respiratory fungal infection

Aspergillus fumigatus forms ubiquitous airborne conidia that humans inhale on a daily basis. Although respiratory fungal infection activates the adaptor proteins CARD9 and MyD88 via C-type lectin, Toll-like, and interleukin-1 family receptor signals, defining the temporal and spatial pattern of MyD88- and CARD9-coupled signals in immune activation and fungal clearance has been difficult to achieve. Herein, we demonstrate that MyD88 and CARD9 act in two discrete phases and in two cellular compartments to direct chemokine- and neutrophil-dependent host defense. The first phase depends on MyD88 signaling because genetic deletion of MyD88 leads to delayed induction of the neutrophil chemokines CXCL1 and CXCL5, delayed neutrophil lung trafficking, and fatal pulmonary damage at the onset of respiratory fungal infection. MyD88 expression in lung epithelial cells restores rapid chemokine induction and neutrophil recruitment via interleukin-1 receptor signaling. Exogenous CXCL1 administration reverses murine mortality in MyD88-deficient mice. The second phase depends predominately on CARD9 signaling because genetic deletion of CARD9 in radiosensitive hematopoietic cells interrupts CXCL1 and CXCL2 production and lung neutrophil recruitment beyond the initial MyD88-dependent phase. Using a CXCL2 reporter mouse, we show that lung-infiltrating neutrophils represent the major cellular source of CXCL2 during CARD9-dependent recruitment. Although neutrophil-intrinsic MyD88 and CARD9 function are dispensable for neutrophil conidial uptake and killing in the lung, global deletion of both adaptor proteins triggers rapidly progressive invasive disease when mice are challenged with an inoculum that is sub-lethal for single adapter protein knockout mice. Our findings demonstrate that distinct signal transduction pathways in the respiratory epithelium and hematopoietic compartment partially overlap to ensure optimal chemokine induction, neutrophil recruitment, and fungal clearance within the respiratory tract.

Our understanding of how epithelial and hematopoietic cells in the lung coordinate immunity against inhaled fungal conidia (spores) remains limited. The mold Aspergillus fumigatus is a major cause of infectious mortality in immune compromised patients. Host defense against A. fumigatus involves the activation of two host signal transducers, MyD88 and CARD9, leading to neutrophil recruitment to the infection site. In this study, we define how MyD88- and CARD9-coupled signals operate in epithelial and hematopoietic compartments to regulate neutrophil-mediated defense against A. fumigatus. Our studies support a two-stage model in which MyD88 activation in epithelial cells, via the interleukin-1 receptor, supports the rapid induction of neutrophil-recruiting chemokines. This process is essential for the first phase of neutrophil recruitment. Mortality observed in MyD88-deficient mice can be significantly reversed by administration of a chemokine termed CXCL1 to infected airways. The second phase of neutrophil recruitment is initiated by CARD9 signaling in hematopoietic cells. Loss of both phases of chemokine induction and neutrophil recruitment dramatically increases murine susceptibility to tissue-invasive disease. In sum, our study defines a temporal sequence of events, initiated by interleukin-1 receptor/MyD88 signaling in the pulmonary epithelium and propagated by CARD9 signaling in hematopoietic cells, that induces protective immunity against inhaled fungal conidia.

The role of interleukin-1 family members in the host defence against Aspergillus fumigatus

The interleukin (IL)-1 family consists of 11 members, which all play significant roles in regulating inflammatory responses in the host. IL-1α and IL-1β exert potent pro-inflammatory effects and are key players in the recruitment of neutrophils to the site of inflammation. Protective anti-Aspergillus host responses during the early stages of invasive aspergillosis are critically dependent on neutrophil recruitment, and several lines of evidence support that there is an important role for IL-1 in this process. However, IL-1-mediated inflammation needs to be tightly regulated, since uncontrolled inflammation can result in inflammatory pathology and thereby be detrimental for the host. Aspergillus-induced IL-1-mediated inflammation could therefore be amendable for IL-1 blockade under specific circumstances. This review describes the current understanding of the role of IL-1 family members in the host response against Aspergillus fumigatus and highlights the importance of balanced IL-1 responses in aspergillosis.

Immunoevasive Aspergillus virulence factors

Individuals with structural lung disease or defective immunity are predisposed to Aspergillus-associated disease. Manifestations range from allergic to cavitary or angio-invasive syndromes. Despite daily spore inhalation, immunocompetence facilitates clearance through initiation of innate and adaptive host responses. These include mechanical barriers, phagocyte activation, antimicrobial peptide release and pattern recognition receptor activation. Adaptive responses include Th1 and Th2 approaches. Understanding Aspergillus virulence mechanisms remains critical to the development of effective research and treatment strategies to counteract the fungi. Major virulence factors relate to fungal structure, protease release and allergens; however, mechanisms utilized to evade immune recognition continue to be important in establishing infection. These include the fungal rodlet layer, dihydroxynaphthalene-melanin, detoxifying systems for reactive oxygen species and toxin release. One major immunoevasive toxin, gliotoxin, plays a key role in mediating Aspergillus-associated colonization in the context of cystic fibrosis. Here, it down-regulates vitamin D receptor expression which following itraconazole therapy is rescued concurrent with decreased Th2 cytokine (IL-5 and IL-13) concentrations in the CF airway. This review focuses on the interaction between Aspergillus pathogenic mechanisms, host immune responses and the immunoevasive strategies employed by the organism during disease states such as that observed in cystic fibrosis.

Reprogramming tumor-infiltrating dendritic cells for CD103+ CD8+ mucosal T-cell differentiation and breast cancer rejection

Our studies showed that tumor-infiltrating dendritic cells (DC) in breast cancer drive inflammatory Th2 (iTh2) cells and protumor inflammation. Here, we show that intratumoral delivery of the β-glucan curdlan, a ligand of dectin-1, blocks the generation of iTh2 cells and prevents breast cancer progression in vivo. Curdlan reprograms tumor-infiltrating DCs via the ligation of dectin-1, enabling the DCs to become resistant to cancer-derived thymic stromal lymphopoietin (TSLP), to produce IL-12p70, and to favor the generation of Th1 cells. DCs activated via dectin-1, but not those activated with TLR-7/8 ligand or poly I:C, induce CD8+ T cells to express CD103 (αE integrin), a ligand for cancer cells, E-cadherin. Generation of these mucosal CD8+ T cells is regulated by DC-derived integrin αvβ8 and TGF-β activation in a dectin-1-dependent fashion. These CD103+ CD8+ mucosal T cells accumulate in the tumors, thereby increasing cancer necrosis and inhibiting cancer progression in vivo in a humanized mouse model of breast cancer. Importantly, CD103+ CD8+ mucosal T cells elicited by reprogrammed DCs can reject established cancer. Thus, reprogramming tumor-infiltrating DCs represents a new strategy for cancer rejection.

The interleukin-1 family: back to the future

Interleukin-1 (IL-1) is a central mediator of innate immunity and inflammation. The IL-1 family includes seven ligands with agonist activity (IL-1α and IL-1β, IL-18, IL-33, IL-36α, IL-36β, IL-36γ), three receptor antagonists (IL-1Ra, IL-36Ra, IL-38), and an anti-inflammatory cytokine (IL-37). Members of the IL-1 Receptor (IL-1R) family include six receptor chains forming four signaling receptor complexes, two decoy receptors (IL-1R2, IL-18BP), and two negative regulators (TIR8 or SIGIRR, IL-1RAcPb). A tight regulation via receptor antagonists, decoy receptors, and signaling inhibitors ensures a balance between amplification of innate immunity and uncontrolled inflammation. All cells of the innate immune system express and/or are affected by IL-1 family members. Moreover, IL-1 family members play a key role in the differentiation and function of polarized innate and adaptive lymphoid cells. Here we will review the key properties of IL-1 family members, with emphasis on pathways of negative regulation and orchestration of innate and adaptive immunity.

Opposing Functions of Classic and Novel IL-1 Family Members in Gut Health and Disease

In addition to their well-established role(s) in the pathogenesis of gastrointestinal (GI)-related inflammatory disorders, including inflammatory bowel disease (IBD) and inflammation-associated colorectal cancer (CRC), emerging evidence confirms the critical involvement of the interleukin-1 (IL-1) cytokine family and their ligands in the maintenance of normal gut homeostasis. In fact, the paradigm that IBD occurs in two distinct phases is substantiated by the observation that classic IL-1 family members, such as IL-1, the IL-1 receptor antagonist (IL-1Ra), and IL-18, possess dichotomous functions depending on the phase of disease, as well as on their role in initiating vs. sustaining chronic gut inflammation. Another recently characterized IL-1 family member, IL-33, also possesses dual functions in the gut. IL-33 is upregulated in IBD and potently induces Th2 immune responses, while also amplifying Th1-mediated inflammation. Neutralization studies in acute colitis models, however, have yielded controversial results and recent reports suggest a protective role of IL-33 in epithelial regeneration and mucosal wound healing. Finally, although little is currently known regarding the potential contribution of IL-36 family members in GI inflammation/homeostasis, another IL-1 family member, IL-37, is emerging as a potent anti-inflammatory cytokine with the ability to down-regulate colitis. This new body of information has important translational implications for both the prevention and treatment of patients suffering from IBD and inflammation-associated CRC.

New Insights in the Immunobiology of IL-1 Family Members

The interleukin-1 (IL 1) family of ligands is associated with acute and chronic inflammation, and plays an essential role in the non-specific innate response to infection. The biological properties of IL 1 family ligands are typically pro-inflammatory. The IL 1 family has 11 family members and can be categorized into subfamilies according to the length of their precursor and the length of the propiece for each precursor (Figure 1). The IL 1 subfamily consists of IL 1α, IL 1β, and IL 33, with the longest propieces of the IL 1 family. IL 18 and IL 37 belong to the IL 18 subfamily and contain smaller propieces than IL 1 and IL-33. Since IL 37 binds to the IL 18Rα chain it is part of the IL 18 subfamily, however it remains to be elucidated how the propiece of IL 37 is removed. IL 36α, β, and γ as well as IL 36 Ra belong to the IL 36 subfamily. In addition, IL 38 likely belongs to this family since it has the ability to bind to the IL 36R. The IL 36 subfamily has the shortest propiece. The one member of the IL 1 family that cannot be categorized in these subfamilies is IL 1 receptor antagonist (IL 1Ra), which has a signal peptide and is readily secreted. In the present review we will describe the biological functions of the IL-1F members and new insights in their biology.