Involvement of IL-26 in bronchiolitis obliterans syndrome but not in acute rejection after lung transplantation

BACKGROUND

 The main long-term complication after lung transplantation is bronchiolitis obliterans syndrome (BOS), a deadly condition in which neutrophils may play a critical pathophysiological role. Recent studies show that the cytokine interleukin IL-26 can facilitate neutrophil recruitment in response to pro-inflammatory stimuli in the airways. In this pilot study, we characterized the local involvement of IL-26 during BOS and acute rejection (AR) in human patients.

METHOD

 From a biobank containing bronchoalveolar lavage (BAL) samples from 148 lung transplant recipients (LTR), clinically-matched patient pairs were identified to minimize the influence of clinical confounders. We identified ten pairs (BOS/non-BOS) with BAL samples harvested on three occasions for our longitudinal investigation and 12 pairs of patients with and without AR. The pairs were matched for age, gender, preoperative diagnosis, type of and time after surgery. Extracellular IL-26 protein was quantified in cell-free BAL samples using an enzyme-linked immunosorbent assay. Intracellular IL-26 protein in BAL cells was determined using immunocytochemistry (ICC) and flow cytometry.

RESULTS

 The median extracellular concentration of IL-26 protein was markedly increased in BAL samples from patients with BOS (p < 0.0001) but not in samples from patients with AR. Intracellular IL-26 protein was confirmed in alveolar macrophages and lymphocytes (through ICC and flow cytometry) among BAL cells obtained from BOS patients.

CONCLUSIONS

 Local IL-26 seems to be involved in BOS but not AR, and macrophages as well as lymphocytes constitute cellular sources in this clinical setting. The enhancement of extracellular IL-26 protein in LTRs with BOS warrants further investigation of its potential as a target for diagnosing, monitoring, and treating BOS.

IL-26 promotes the pathogenesis of malignant pleural effusion by enhancing CD4+ IL-22+ T-cell differentiation and inhibiting CD8+ T-cell cytotoxicity

IL-26 is a newly discovered IL-10 cytokine family member mainly secreted by Th17 cells. However, the relationship between IL-26 and lung cancer remains unclear. The present study reported that IL-26 is involved in the production and promotion of malignant pleural effusion (MPE) for the first time. The concentrations of IL-26 and several Th17-related cytokines in MPE and peripheral blood (PB) from MPE patients were measured. IL-26, IL-10, and IL-6 were elevated in MPE compared to PB. The cell resource of IL-26 was primary Th17 cells measured by flow cytometry, whereas Tc17 cells and macrophages could also contribute to higher concentration of IL-26 in MPE. Abundant IL-6 and IL-23 in MPE could promote the frequency of IL-26 expressed by CD4+ T cells through phosphorylating STAT3 signaling pathway and promoting the expression of a specific Th17 lineage marker RORγt subsequently. IL-26 could selectively increase Th22 proportion through up-regulating the percentage of Ki-67 expressed by CD4+ T cells and the expression of IL-22 secreted by memory CD4+ T cells. In addition, IL-26 could decrease secretion of granzyme B. The tumor-killing activity of CD8+ T cells were inhibited as well when cocultured with malignant cells. Furthermore, the accumulation of IL-26 protein in MPE predicted poor patient survival. In summary, our results indicated that IL-26 was involved in the pathogenesis of MPE by exerting its impacts on both CD4+ T cells and CD8+ T cells.

Promotion of osteoclastogenesis by IL-26 in rheumatoid arthritis

Background

The inflammatory cascade in the rheumatoid arthritis (RA) synovium is modulated by a variety of cytokine and chemokine networks; however, the roles of IL-26, in RA pathogenesis, are poorly defined. Here, we investigated the functional role of interleukin-26 (IL)-26 in osteoclastogenesis in RA.

Methods

We analyzed levels of IL-20 receptor subunit A (IL-20RA), CD55, and receptor activator of nuclear factor kappaB (NF-κB) ligand (RANKL) in RA fibroblast-like synoviocytes (FLSs) using confocal microscopy. Recombinant human IL-26-induced RANKL expression in RA-FLSs was examined using real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). Human peripheral blood monocytes were cultured with macrophage colony-stimulating factor (M-CSF) and IL-26, after which osteoclastogenesis was evaluated by counting the number of tartrate-resistant acid phosphatase-positive multinucleated cells. Additionally, osteoclastogenesis was evaluated by monocytes co-cultured with IL-26-prestimulated FLSs.

Results

The expression of IL-20RA in RA-FLSs was higher than that in osteoarthritis-FLSs. Additionally, in IL-26-pretreated RA-FLSs, the expression of IL-20RA (but not IL-10 receptor subunit B) and RANKL increased in a dose-dependent manner, with IL-26-induced RANKL expression reduced by IL-20RA knockdown. Moreover, IL-26-induced RANKL expression was significantly downregulated by inhibition of signal transducer and activator of transcription 1, mitogen-activated protein kinase, and NF-κB signaling. Furthermore, IL-26 promoted osteoclast differentiation from peripheral blood monocytes in the presence of low dose of RANKL, with IL-26 exerting an additive effect. Furthermore, co-culture of IL-26-pretreated RA-FLSs with peripheral blood monocytes also increased osteoclast differentiation in the absence of addition of RANKL.

Conclusions

IL-26 regulated osteoclastogenesis in RA through increased RANKL expression in FLSs and direct stimulation of osteoclast differentiation. These results suggest the IL-26/IL-20RA/RANKL axis as a potential therapeutic target for addressing RA-related joint damage.

Characterization of novel anti-IL-26 neutralizing monoclonal antibodies for the treatment of inflammatory diseases including psoriasis

Interleukin (IL)-26, known as a Th17 cytokine, acts on various cell types and has multiple biological functions. Although its precise role still remains to be elucidated, IL-26 is suggested to be associated with the pathology of diverse chronic inflammatory diseases such as psoriasis, inflammatory bowel diseases and rheumatoid arthritis. To develop novel neutralizing anti-human IL-26 monoclonal antibodies (mAbs) for therapeutic use in the clinical setting, we immunized mice with human IL-26 protein. Hybridomas producing anti-IL-26 mAbs were screened for various in vitro functional assays, STAT3 phosphorylation and antibiotic assays. Although the IL-20RA/IL-10RB heterodimer is generally believed to be the IL-26 receptor, our data strongly suggest that both IL-20RA-dependent and -independent pathways are involved in IL-26-mediated stimulation. We also investigated the potential therapeutic effect of anti-IL-26 mAbs in the imiquimod-induced psoriasis-like murine model using human IL-26 transgenic mice. These screening methods enabled us to develop novel neutralizing anti-human IL-26 mAbs. Importantly, administration of IL-26-neutralizing mAb did not have an effect on the antimicrobial activity of IL-26. Taken together, our data strongly suggest that our newly developed anti-human IL-26 mAb is a potential therapeutic agent for the treatment of diverse chronic inflammatory diseases including psoriasis.

Interleukin-26 upregulates interleukin-22 production by human CD4+ T cells in tuberculous pleurisy

IL-26 is a potentially important player in host defense and may be a pathogenic factor in the chronic inflammatory disorders of humans. However, the involvement of IL-26 in tuberculous pleural effusion (TPE) has not been investigated. The concentration of IL-26 was determined in pleural fluids and sera from patients with pleural effusions. Flow cytometry was performed to identify the cell origin of IL-26. The effects of tuberculosis-specific antigen (ESAT-6/CFP-10) on IL-26 expression of CD4+ T cell were explored. The impacts of IL-26 on modulating CD4+ T cell polarization were also investigated. The concentrations of IL-26 were much higher in tuberculous, malignant, and infectious PE than those in the corresponding serum. The expression of IL-26 on CD4+ T cells was much higher in tuberculous PE than those in the corresponding serum, and pleural Th1 and Th17 cells might be the major cell sources of IL-26. The addition of ESAT-6/CFP-10 to CD4+ T cells led to increasing the number of IL-26-producing CD4+ T cells and IL-26 expression on Th1 and Th17 cells. IL-26 could induce the differentiation and generation of IL-22 by memory and naive CD4+ T cells. IL-26 also upregulated the mRNA encoding CC-chemokine ligand 20 (CCL20) and CCL22 by mononuclear cells isolated from TPE. This study implies that pleural Th1 and Th17 cells are the major cell sources of IL-26, which could induce the differentiation and generation of Th22 cells by CD4+ T cells, suggesting the involvement of IL-26 in the pathogenesis of human TPE. KEY MESSAGES: IL-26 is overexpressed in TPE patients and presents a higher concentration in pleural effusion than the corresponding peripheral blood. Pleural Th1 and Th17 cells might be the major cell sources of IL-26 in TPE patients. IL-26 promotes IL-22 secretion and Th22 generation by CD4+ T cells isolated from TPE patients. IL-26 may play an active role in the pathogenesis of tuberculous pleurisy.

Expression of Interleukin-26 is upregulated in inflammatory bowel disease

AIM

To investigate interleukin (IL)-26 expression in the inflamed mucosa of patients with inflammatory bowel disease (IBD) and the function of IL-26.

METHODS

Human colonic subepithelial myofibroblasts (SEMFs) were isolated from colon tissue surgically resected. The expression of IL-26 protein and its receptor complex was analyzed by immunohistochemistry. The gene expression induced by IL-26 was evaluated by real-time polymerase chain reaction. Intracellular signaling pathways were evaluated by immunoblotting and specific small interfering (si) RNA transfection.

RESULTS

The mRNA and protein expression of IL-26 were significantly enhanced in the inflamed mucosa of patients with IBD. IL-26 receptor complex was expressed in colonic SEMFs in vivo and in vitro. IL-26 stimulated the mRNA expression of IL-6 and IL-8 in colonic SEMFs. The inhibitors of mitogen-activated protein kinases and phosphoinositide 3-kinase, and siRNAs for signal transducers and activator of transcription 1/3, nuclear factor-kappa B and activator protein-1 significantly reduced the mRNA expression of IL-6 and IL-8 induced by IL-26.

CONCLUSION

These results suggest that IL-26 plays a role in the pathophysiology of IBD through induction of inflammatory mediators.