Expression of Interleukin-26 is upregulated in inflammatory bowel disease

Interleukin-26 expression in tuberculosis disease and its regulatory effect in macrophage polarization and intracellular elimination of Mycobacterium tuberculosis

Tuberculosis(TB), an infectious disease caused by Mycobacterium tuberculosis (Mtb) infections, remains the leading cause of mortality from a single infectious agent globally. The progression of tuberculosis disease is contingent upon the complex interplay between the host's immune system and the pathogen Mtb. Interleukin-26 (IL-26), the most recently identified cytokine belonging to the IL-10 family, exhibits both extracellular antimicrobial properties and pro-inflammatory functions. However, the precise role of IL-26 in the host immune defense against Mtb infections and intracellular killing remains largely unexplored. In this study, we observed significantly elevated IL-26 mRNA expression in peripheral blood mononuclear cells of active-TB patients compared to healthy individuals. Conversely, circulating IL-26 levels in the plasma of adult TB patients were markedly lower than those of healthy cohorts. We purified recombinant IL-26 from an E. coli expression system using the Ni-NTA resin. Upon stimulations with the recombinant IL-26, human THP1 cells exhibited rapid morphological changes characterized by increased irregular spindle shape and formation of granular structures. Treating THP1 cells with IL-26 can also lead to heightened expressions of CD80, TNF-α, and iNOS but not CD206 and Arg1 in these cells, indicating an M1 macrophage differentiation phenotype. Furthermore, our investigations revealed a dose-dependent escalation of reactive oxygen species production, decreased mitochondrial membrane potential, and enhanced autophagy flux activity in THP1 macrophages following IL-26 treatment. Moreover, our results demonstrated that IL-26 contributed to the elimination of intracellular Mycobacterium tuberculosis via orchestrated ROS production. In conclusion, our findings elucidated the role of IL-26 in the development of tuberculosis and its contributions to intracellular bacilli killing by macrophages through the induction of M1-polarization and ROS production. These insights may have significant implications for understanding the pathogenesis of tuberculosis and developing novel therapeutic strategies.

A Comprehensive Network Map of Interleukin-26 Signaling Pathway

Interleukin-26 (IL-26) is a cytokine that belongs to the IL-20 subfamily and is primarily expressed in T helper 1 cells and Th17 memory CD4+ cells. Its receptor complex, consisting of IL-20R1 and IL-10R2, activates a signaling pathway involving several proteins such as Janus kinase 1 and tyrosine-protein kinase, signal transducer and activator of transcription (STAT) 1, and STAT3. This leads to the initiation of downstream signaling cascades that play a crucial role in various biological processes, including inflammation, immune response regulation, atopic dermatitis, macrophage differentiation, osteoclastogenesis, antibacterial host defense, anti-apoptosis, and tumor growth. In this study, we curated literature data pertaining to IL-26 signaling. The curated map includes a total of seven activation/inhibition events, 16 catalysis events, 33 gene regulation events, 25 protein expression types, two transport events, and three molecular associations.

Immunobiology of IL-26

T helper 17 (Th17) cells produce a set of cytokines that include IL-17 family members, IL-21, IL-22, and IL-26. These cytokines all contribute to the classic function of Th17 cells in combatting extracellular infection and promoting inflammation in autoimmune diseases. However, of the Th17 cytokines, only IL-26 has direct antimicrobial activity against microbes and can activate a broad range of immune cells through its ability to bind DNA and trigger pattern recognition receptors. It is noteworthy that IL-26 is produced by mammalian cells, including human Th17 cells, but is absent in rodents. As such, IL-26 is a potential therapeutic target to augment host immune responses against microbial pathogens but also to prevent inflammation and tissue damage in a variety of autoimmune diseases.

Human neutrophils drive skin autoinflammation by releasing interleukin (IL)-26

Autoinflammation is a sterile inflammatory process resulting from increased neutrophil infiltration and overexpression of IL-1 cytokines. The factors that trigger these events are, however, poorly understood. By investigating pustular forms of psoriasis, we show that human neutrophils constitutively express IL-26 and abundantly release it from granular stores upon activation. In pustular psoriasis, neutrophil-derived IL-26 drives the pathogenic autoinflammation process by inducing the expression of IL-1 cytokines and chemokines that further recruit neutrophils. This occurs via activation of IL-26R in keratinocytes and via the formation of complexes between IL-26 and microbiota DNA, which trigger TLR9 activation of neutrophils. Thus our findings identify neutrophils as an important source of IL-26 and point to IL-26 as the key link between neutrophils and a self-sustaining autoinflammation loop in pustular psoriasis.

The role of Th17 cells in inflammatory bowel disease and the research progress

Th17 cells play an important role in the abnormal immune response in inflammatory bowel disease (IBD) and are involved in the development and progression of inflammation and fibrosis. An increasing amount of data has shown that gut microbes are important parts of intestinal immunity and regulators of Th17 cellular immunity. Th17 cell differentiation is regulated by intestinal bacteria and cytokines, and Th17 cells regulate the intestinal mucosal immune microenvironment by secreting cytokines, such as IL-17, IL-21, and IL-26. Solid evidence showed that, regarding the treatment of IBD by targeting Th17 cells, the therapeutic effect of different biological agents varies greatly. Fecal bacteria transplantation (FMT) in the treatment of IBD has been a popular research topic in recent years and is safe and effective with few side effects. To further understand the role of Th17 cells in the progression of IBD and associated therapeutic prospects, this review will discuss the progress of related research on Th17 cells in IBD by focusing on the interaction and immune regulation between Th17 cells and gut microbiota.

Interleukin-26 Expression in Inflammatory Bowel Disease and Its Immunoregulatory Effects on Macrophages

Background and Aim

Interleukin-26 (IL-26) has been implicated in several chronic inflammatory diseases. However, its role in inflammatory bowel disease (IBD) remains to be elucidated. We aimed to investigate IL-26 expression in IBD and its immunoregulatory effects on macrophages.

Methods

We assessed IL-26 expression in the intestinal mucosa and blood samples of IBD patients and healthy controls (HC). The associations between the clinical characteristics of IBD and IL-26 expression levels in serum and peripheral blood mononuclear cells (PBMCs) were investigated. In addition, the transcriptional changes in THP-1 macrophages exposed to IL-26 were determined by RNA sequencing and validated with qRT-PCR, ELISA and western blots.

Results

Compared with HC, in IBD patients, IL-26 expression levels were elevated in the inflamed intestinal mucosa, and reduced in serum and PBMCs. IL-26 mRNA levels in PBMCs, but not serum IL-26 levels, were inversely correlated with disease activity in IBD. Furthermore, IL-26 mRNA levels in PBMCs were significantly lower in patients with complicated Crohn's disease. A total of 1,303 differentially expressed protein-coding genes were identified between untreated and IL-26-treated macrophages. The up-regulated genes showed enrichment in some inflammatory and immune-related processes and pathways. Additionally, GSEA showed that neutrophil, monocyte, and lymphocyte chemotaxis was significantly enriched in IL-26-treated macrophages. Further validation revealed that IL-26 promotes the secretion of multiple inflammatory cytokines and chemokines and upregulates the expression of adhesion molecules, MMP-8, and MMP-9 while inhibiting MMP-1 in macrophages.

Conclusion

Compared with HC, in IBD patients, IL-26 levels were elevated in the inflamed intestinal mucosa, and reduced in the peripheral blood. The transcriptional changes in macrophages exposed to IL-26 suggest that IL-26 may amplify the aberrant immune response in IBD by activating macrophages.

IL-26 inhibits hepatitis C virus replication in hepatocytes

BACKGROUND & AIMS

Interleukin-26 (IL-26) is a proinflammatory cytokine that has properties atypical for a cytokine, such as direct antibacterial activity and DNA-binding capacity. We previously observed an accumulation of IL-26 in fibrotic and inflammatory lesions in the livers of patients with chronic HCV infection and showed that infiltrating CD3⁺ lymphocytes were the principal source of IL-26. Surprisingly, IL-26 was also detected in the cytoplasm of hepatocytes from HCV-infected patients, even though these cells do not produce IL-26, even when infected with HCV. Based on this observation and possible interactions between IL-26 and nucleic acids, we investigated the possibility that IL-26 controlled HCV infection independently of the immune system.

METHODS

We evaluated the ability of IL-26 to interfere with HCV replication in hepatocytes and investigated the mechanisms by which IL-26 exerts its antiviral activity.

RESULTS

We showed that IL-26 penetrated HCV-infected hepatocytes, where it interacted directly with HCV double-stranded RNA replication intermediates, thereby inhibiting viral replication. IL-26 interfered with viral RNA-dependent RNA polymerase activity, preventing the de novo synthesis of viral genomic single-stranded RNA.

CONCLUSIONS

These findings reveal a new role for IL-26 in direct protection against HCV infection, independently of the immune system, and increase our understanding of the antiviral defense mechanisms controlling HCV infection. Future studies should evaluate the possible use of IL-26 for treating other chronic disorders caused by RNA viruses, for which few treatments are currently available, or emerging RNA viruses.

LAY SUMMARY

This study sheds new light on the body's arsenal for controlling hepatitis C virus (HCV) infection and identifies interleukin-26 (IL-26) as an antiviral molecule capable of blocking HCV replication. IL-26, which has unique biochemical and structural characteristics, penetrates infected hepatocytes and interacts directly with viral RNA, thereby blocking viral replication. IL-26 is, therefore, a new player in antiviral defenses, operating independently of the immune system. It is of considerable potential interest for treating HCV infection and other chronic disorders caused by RNA viruses for which few treatments are currently available, and for combating emerging RNA viruses.

Clinical and Immunological Factors Associated with Recommended Trough Levels of Adalimumab and Infliximab in Patients with Crohn's Disease

Introduction: Up to 40% of patients with Crohn's disease do not respond to treatment with anti-TNF or lose response after the initial benefit. Low drug concentrations have been proposed as the main predictor of treatment failure. Our aim was to study the immunological profile and clinical evolution of patients with Crohn's disease according to the anti-TNF dose and serum trough levels. Methods: Crohn's disease patients in remission treated with infliximab or adalimumab at stable doses for at least for 3 months were included. Serum levels of anti-TNF, TNF-α, interferon-γ, and interleukin IL-12, IL-10, and IL-26 were determined in blood samples taken just before drug administration. Patients were classified according to anti-TNF levels below, within, or above the target level range and the use of intensified doses. Clinical evolution at 6 months was analyzed. Results: A total of 62 patients treated with infliximab (8 on intensified schedule) and 49 treated with adalimumab (7 on intensified schedule) were included. All infliximab-treated patients showed levels within the recommended range, but half of adalimumab-treated patients were below the recommended range. A significant negative relationship between body weight and adalimumab levels was observed, especially in patients treated with intensified doses. Patients with infliximab levels over 8 µg/ml presented higher median IL-10 than patients with in-range levels (84.0 pg/ml, interquartile range [IQR] 77.0-84.8 vs. 26.2 pg/mL, IQR 22.6-38.0; p < 0.001), along with lower values of interferon-γ (312.9 pg/ml, IQR 282.7-350.4 vs. 405.6 pg/ml, IQR 352.2-526.6; p = 0.005). Patients receiving intensified versus non-intensified doses of infliximab showed significantly higher IL-26 levels (91.8 pg/ml, IQR 75.6-109.5 vs. 20.5 pg/ml, IQR 16.2-32.2; p = 0.012), irrespective of serum drug levels. Patients with in-range levels of adalimumab showed higher values of IL-10 than patients with below-range levels (43.3 pg/ml, IQR 35.3-54.0 vs. 26.3 pg/ml, IQR 21.6-33.2; p = 0.001). Patients treated with intensified vs regular doses of adalimumab had increased levels of IL-12 (612.3 pg/ml, IQR 570.2-1353.7 vs. 516.4 pg/mL, IQR 474.5-591.2; p = 0.023). Four patients with low adalimumab levels (19%) and four treated with intensified doses were admitted to a hospital during a follow-up compared to none of the patients with levels within the range. Conclusion: Patients with Crohn's disease treated with infliximab and adalimumab exhibit differences in serum levels of cytokines depending on the drug, dose intensification, and steady state trough serum levels.

The Role of Interleukins in the Pathogenesis of Dermatological Immune-Mediated Diseases

Autoimmune inflammatory diseases are primarily characterized by deregulated expression of cytokines, which drive pathogenesis of these diseases. A number of approved and experimental therapies utilize monoclonal antibodies against cytokine proteins. Cytokines can be classified into different families including the interleukins, which are secreted and act on leukocytes, the tumor necrosis factor (TNF) family, as well as chemokine proteins. In this review article, we focus on the interleukin family of cytokines, of which 39 members have been identified to this date. We outline the role of each of these interleukins in the immune system, and various dermatological inflammatory diseases with a focused discussion on the pathogenesis of psoriasis and atopic dermatitis. In addition, we describe the roles of various interleukins in psychiatric, cardiovascular, and gastrointestinal comorbidities. Finally, we review clinical efficacy and safety data from emerging late-phase anti-interleukin therapies under development for psoriasis and atopic dermatitis. Collectively, additional fundamental and clinical research remains necessary to fully elucidate the roles of various interleukin proteins in the pathogenesis of inflammatory dermatologic diseases, and treatment outcomes in patients.

The Kinocidin Interleukin-26 Shows Immediate Antimicrobial Effects Even to Multi-resistant Isolates

The cationic proinflammatory cytokine Interleukin 26 (IL-26) shows antibacterial activity and inhibits the replication of cytomegalovirus and hepatitis C virus. This study evaluates the early microbicidal activities of IL-26 against major bacterial species including multi-resistant variants and Candida albicans. Recombinant IL-26 was bacterially expressed and studied for its microbicidal effects in culture. We show that IL-26 has strong 90% bactericidal activities against Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, and Acinetobacter baumannii. Similarly, IL-26 sensitivity was also detectable in vancomycin-resistant Enterococcus species, methicillin-resistant S. aureus, and carbapenem-resistant A. baumannii clinical isolates. Additionally, a significant, albeit weak fungicidal effect against Candida albicans was observed. Activities against Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa were not detectable. The proinflammatory cytokine and kinocidin IL-26 shows strong bactericidal activities against A. baumannii and, almost selectively, against Gram-positive bacteria.

A comprehensive review of IL-26 to pave a new way for a profound understanding of the pathobiology of cancer, inflammatory diseases and infections

Cytokines are considered vital mediators of the immune system. Down- or upregulation of these mediators is linked to several inflammatory and pathologic situations. IL-26 is referred to as an identified member of the IL-10 family and IL-20 subfamily. Due to having a unique cationic structure, IL-26 exerts diverse functions in several diseases. Since IL-26 is mainly secreted from Th17, it is primarily considered a pro-inflammatory cytokine. Upon binding to its receptor complex (IL-10R1/IL-20R2), IL-26 activates multiple signalling mediators, especially STAT1/STAT3. In cancer, IL-26 induces IL-22-producing cells, which consequently decrease cytotoxic T-cell functions and promote tumour growth through activating anti-apoptotic proteins. In hypersensitivity conditions such as rheumatoid arthritis, multiple sclerosis, psoriasis and allergic disease, this cytokine functions primarily as the disease-promoting mediator and might be considered a biomarker for disease prognosis. Although IL-26 exerts antimicrobial function in infections such as hepatitis, tuberculosis and leprosy, it has also been shown that IL-26 might be involved in the pathogenesis and exacerbation of sepsis. Besides, the involvement of IL-26 has been confirmed in other conditions, including graft-versus-host disease and chronic obstructive pulmonary disease. Therefore, due to the multifarious function of this cytokine, it is proposed that the underlying mechanism regarding IL-26 function should be elucidated. Collectively, it is hoped that the examination of IL-26 in several contexts might be promising in predicting disease prognosis and might introduce novel approaches in the treatment of various diseases.

huARdb: human Antigen Receptor database for interactive clonotype-transcriptome analysis at the single-cell level

T-cell receptors (TCRs) and B-cell receptors (BCRs) are critical in recognizing antigens and activating the adaptive immune response. Stochastic V(D)J recombination generates massive TCR/BCR repertoire diversity. Single-cell immune profiling with transcriptome analysis allows the high-throughput study of individual TCR/BCR clonotypes and functions under both normal and pathological settings. However, a comprehensive database linking these data is not yet readily available. Here, we present the human Antigen Receptor database (huARdb), a large-scale human single-cell immune profiling database that contains 444 794 high confidence T or B cells (hcT/B cells) with full-length TCR/BCR sequence and transcriptomes from 215 datasets. All datasets were processed in a uniform workflow, including sequence alignment, cell subtype prediction, unsupervised cell clustering, and clonotype definition. We also developed a multi-functional and user-friendly web interface that provides interactive visualization modules for biologists to analyze the transcriptome and TCR/BCR features at the single-cell level. HuARdb is freely available at https://huarc.net/database with functions for data querying, browsing, downloading, and depositing. In conclusion, huARdb is a comprehensive and multi-perspective atlas for human antigen receptors.

Prognostic value of IL-26 level in hepatocellular carcinoma tissue in postoperative patients with hepatitis B related hepatocellular carcinoma

BACKGROUND

The current hepatocellular carcinoma (HCC) staging system is not ideal for judging the prognosis of patients after surgical resection, so it is very important to find and identify the patients who are prone to recurrence and carry out targeted intervention. In recent years, the relationship between liver immunity and HCC has become a research hotspot. Interleukin (IL)-26 can predict the prognosis of patients with HCC, but there is a lack of research on the prognosis of patients 5 years after surgery.

AIM

To analyze the prognostic value of IL-26 in HCC tissues of patients with hepatitis B.

METHODS

The preoperative data of hepatitis B related HCC patients who were hospitalized and operated at our hospital from January 2006 to June 2015 were collected. The expression of IL-26 in resected HCC tissues was measured by immunohistochemistry and based on the median expression level of IL-26, the patients were divided into either a high expression group or a low expression group. The 5-year overall survival (OS) and progression free survival (PFS) were compared between the two groups by Kaplan-Meier method.

RESULTS

The percentages of patients with a tumor size > 5 cm, microvascular invasion, and TNM stage III/IV disease in the high expression group were significantly higher than those of the low expression group (P = 0.026, 0.009, and P =0.045, respectively). High expression of IL-26 (hazard ratio [HR] = 1.667, P = 0.022), tumor size > 5 cm (HR = 1.096, P = 0.002), and microvascular invasion (HR = 2.696, P = 0.006) were the influencing factors of PFS in patients with HCC resection. High expression of IL-26 (HR = 1.643, P = 0.041) and microvascular invasion (HR = 3.303, P = 0.016) were independent prognostic factors for OS in patients with HCC resection. PFS and OS in patients with high expression of IL-26 were worse than those with low expression.

CONCLUSION

The expression of IL-26 in HCC tissue correlates with the OS and PFS of patients with hepatitis B-related liver cancer after resection.

Inflammation status modulates the effect of host genetic variation on intestinal gene expression in inflammatory bowel disease

More than 240 genetic risk loci have been associated with inflammatory bowel disease (IBD), but little is known about how they contribute to disease development in involved tissue. Here, we hypothesized that host genetic variation affects gene expression in an inflammation-dependent way, and investigated 299 snap-frozen intestinal biopsies from inflamed and non-inflamed mucosa from 171 IBD patients. RNA-sequencing was performed, and genotypes were determined using whole exome sequencing and genome wide genotyping. In total, 28,746 genes and 6,894,979 SNPs were included. Linear mixed models identified 8,881 independent intestinal cis-expression quantitative trait loci (cis-eQTLs) (FDR < 0.05) and interaction analysis revealed 190 inflammation-dependent intestinal cis-eQTLs (FDR < 0.05), including known IBD-risk genes and genes encoding immune-cell receptors and antibodies. The inflammation-dependent cis-eQTL SNPs (eSNPs) mainly interact with prevalence of immune cell types. Inflammation-dependent intestinal cis-eQTLs reveal genetic susceptibility under inflammatory conditions that can help identify the cell types involved in and the pathways underlying inflammation, knowledge that may guide future drug development and profile patients for precision medicine in IBD.

Single-cell atlas of colonic CD8+ T cells in ulcerative colitis

Colonic antigen-experienced lymphocytes such as tissue-resident memory CD8+ T cells can respond rapidly to repeated antigen exposure. However, their cellular phenotypes and the mechanisms by which they drive immune regulation and inflammation remain unclear. Here we compiled an unbiased atlas of human colonic CD8+ T cells in health and ulcerative colitis (UC) using single-cell transcriptomics with T-cell receptor repertoire analysis and mass cytometry. We reveal extensive heterogeneity in CD8+ T-cell composition, including expanded effector and post-effector terminally differentiated CD8+ T cells. While UC-associated CD8+ effector T cells can trigger tissue destruction and produce tumor necrosis factor (TNF)-α, post-effector cells acquire innate signatures to adopt regulatory functions that may mitigate excessive inflammation. Thus, we identify colonic CD8+ T-cell phenotypes in health and UC, define their clonal relationships and characterize terminally differentiated dysfunctional UC CD8+ T cells expressing IL-26, which attenuate acute colitis in a humanized IL-26 transgenic mouse model.

KLRG1 and CD103 Expressions Define Distinct Intestinal Tissue-Resident Memory CD8 T Cell Subsets Modulated in Crohn's Disease

Intestinal tissue-resident memory CD8 T cells (Trm) are non-recirculating effector cells ideally positioned to detect and react to microbial infections in the gut mucosa. There is an emerging understanding of Trm cell differentiation and functions, but their implication in inflammatory bowel diseases, such as Crohn's disease (CD), is still unknown. Here, we describe CD8 cells in the human intestine expressing KLRG1 or CD103, two receptors of E-cadherin. While CD103 CD8 T cells are present in high numbers in the mucosa of CD patients and controls, KLRG1 CD8 T cells are increased in inflammatory conditions. Mucosal CD103 CD8 T cells are more responsive to TCR restimulation, but KLRG1 CD8 T cells show increased cytotoxic and proliferative potential. CD103 CD8 T cells originate mostly from KLRG1 negative cells after TCR triggering and TGFβ stimulation. Interestingly, mucosal CD103 CD8 T cells from CD patients display major changes in their transcriptomic landscape compared to controls. They express Th17 related genes including CCL20, IL22, and IL26, which could contribute to the pathogenesis of CD. Overall, these findings suggest that CD103 CD8 T cells in CD induce a tissue-wide alert increasing innate immune responses and recruitment of effector cells such as KLRG1 CD8 T cells.

Sputum IL-26 Is Overexpressed in Severe Asthma and Induces Proinflammatory Cytokine Production and Th17 Cell Generation: A Case-Control Study of Women

Objective

Asthma inflammation is a complex pathway involving numerous mediators. Interleukin-26 (IL-26), a member of the IL-10 cytokine family, is abundant in human airways and induces the production of proinflammatory cytokines. Our aim was to investigate the possible role of IL-26 in severe asthma. We analysed the expression of IL-26 in severe asthma both in peripheral blood and induced sputum.

Patients and Methods

A total of 50 adult women with severe asthma were recruited and compared to 30 healthy controls (HC). Serum and sputum fluid (SF) levels of IL-26 and IL-17 were defined by ELISA. IL-26 mRNA expression and IL-26 protein were analysed using RT-PCR and Western blot. In vitro, we studied the effect of recombinant IL-26 (rIL-26) and SF-IL-26 on cultured CD4⁺ T cells and monocytes, comparing patients and controls.

Results

Concentrations of IL-26 are higher in serum and induced sputum of asthmatic patients than in HC. Moreover, IL-26 protein and mRNA expression were significantly elevated in asthma sputum cells compared to PBMCs. We observed a positive correlation between body mass index (BMI) and sputum fluid IL-26, while the correlation between IL-26 and lung function tests (FEV1% and FEV1/FVC ratio) was negative. IL-17A was highly expressed in SF and correlated positively with IL-26. In patients’ sputum IL-26 and IL-17A were significantly associated with neutrophils. Stimulation of cultured CD4⁺ T cells with monocytes by recombinant IL-26 promoted the generation of RORγt⁺ Th17⁺ cells inducing the production of IL-17A, IL-1β, IL-6 and TNF-α cytokines. IL-26 expressed in SF was biologically active and induced IL-17 secretion in the presence of IL-1β and IL-6 cytokines.

Conclusion

These findings show that IL-26 is highly produced in asthmatic sputum, induces pro-inflammatory cytokine secretion by monocytes/macrophages, and favours Th17 cell generation. IL-26 thereby appears as a novel pro-inflammatory cytokine, produced locally in the airways that may constitute a promising target to treat asthma inflammatory process.

The serum interleukin-26 level is a potential biomarker for chronical hepatitis B

Proinflammatory interleukin-26 (IL-26) is involved in chronic inflammation; however, the role of IL-26 in chronic hepatitis B (CHB) remains unknown.In this study, serum IL-26 was quantified in a cohort of CHB patients at baseline and during telbivudine (LdT) treatment.Our results showed that the serum IL-26 level was significantly elevated in CHB patients compared with that in healthy controls and was time-dependently decreased during LdT treatment, accompanying hepatitis B e antigen (HBeAg) seroconversion and reduced serum levels of hepatitis B virus (HBV) DNA, aspartate transaminase, and alanine transaminase across baseline and treatment. In addition, the serum level of IL-26 exhibited a similar declining trend to that of T helper 17 (Th17) cell-secreted IL-17 during LdT treatment in CHB patients. The percentage of IL-26-expressing CD4 cells was significantly higher than that of IL-26-expressing CD4 cells isolated from the peripheral blood mononuclear cells of CHB patients, suggesting that serum IL-26 might be mainly released from CD4 T cells. Furthermore, the baseline mRNA levels of IL-26 and orphan nuclear receptor RORγt-an important transcription factor expressed by Th17 cells-were positively correlated and displayed the same declining trend across the baseline and LdT treatment in CHB patients, suggesting that Th17 cells could be a possible cellular source of the increased serum IL-26 in CHB patients.Taken together, our results suggest that serum IL-26, possibly produced by Th17 CD4 cells, is a novel and potential biomarker for CHB prognosis and treatment.

Interleukin-26 promotes the proliferation and activation of hepatic stellate cells to exacerbate liver fibrosis by the TGF-β1/Smad2 signaling pathway

Liver fibrosis is a wound-healing process of liver featured by the activation of hepatic stellate cells (HSCs) and the deposition of extra cellular matrix (ECM). Accumulating facts have suggested that interleukin (IL) 26 is involved in the pathogenesis of liver fibrosis by the modulation of HSCs. However, the biological roles of IL-26 in liver fibrosis are still unclear. The present study aimed to determine the effect and mechanism of IL-26 on the proliferation and activation of HSCs in vitro. By cell counting kit (CCK)-8 assay, we observed that IL-26 significantly promoted the proliferation of HSCs by increasing S phase and decreasing G0/G1 phase. Annexin V-FITC/PI double staining showed that IL-26 could suppress the apoptosis of HSCs by inhibition of caspase 3 (CASP3) and Bcl-2 associated X protein (BAX). Furthermore, quantitative real-time PCR (qRT-PCR) assay and western blotting analysis revealed that IL-26 exacerbated the degree of hepatic fibrosis, which was associated with the upregulation of the mRNA levels and protein concentrations of IL-6, IL-10, tumor necrosis factor (TNF)-α, matrix metallopeptidase (MMP)-9, and α-smooth muscle act in (SMA). Mechanistically, western blotting analysis showed that IL-26 upregulated the protein expression levels of transforming growth factor (TGF)-β1 and SMAD family member 2 (Smad2) in HSCs. In summary, the data demonstrated a key role of IL-26 on the proliferation and activation of HSCs in liver fibrosis and the underlying mechanism might be related to the TGF-β1/Smad2 signaling pathway. The finding will provide a proof that targeting IL-26 may be developed as therapeutics for liver fibrosis.

Protective Effect of Spirulina platensis Extract against Dextran-Sulfate-Sodium-Induced Ulcerative Colitis in Rats

Inflammatory bowel disease is a multifactorial inflammatory condition. This study aimed to test the protective effects of Spirulina platensis against ulcerative colitis (UC). UC was induced in thirty-six male Wistar rats by adding dextran sulfate sodium (DSS) to their drinking water, while a control group received only drinking water. UC rats were equally-divided into six groups that received a single oral daily dose of vehicle (DSS), sulfasalazine (SSZ, 50 mg/kg/day), chloroform or the hydroalcoholic extracts of Spirulina platensis (100 or 200 mg/kg/day) for 15 days, and then blood and colon samples were harvested for determination of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), erythrocyte sedimentation rate (ESR), myeloperoxidase (MPO), and histopathology. At the end of the study, compared to time-matched controls, UC rats showed increased TNF-α (1.64-fold), IL-6 (5.73-fold), ESR (3.18-fold), and MPO (1.61-fold), along with loss of body weight (24.73%) and disease activity index (1.767 ± 0.216 vs. 0 ± 0), p < 0.001. These effects were prevented by SSZ treatment (p < 0.001 vs. DSS). The hydroalcoholic extract of Spirulina platensis dose-dependently modulated all DSS-induced inflammatory changes. However, the chloroform extract significantly lowered only IL-6 and ESR, but not TNF-α or MPO levels. The protective effects of the hydroalcoholic extract of Spirulina platensis against experimental UC involved mitigation of DSS-induced inflammation.

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.

A new T helper 17 cytokine in hidradenitis suppurativa: antimicrobial and proinflammatory role of interleukin-26

BACKGROUND

Interleukin (IL)-26 is a signature T helper 17 cytokine described as a proinflammatory and antimicrobial mediator. So far, IL-26 has been reported in several immune-mediated inflammatory diseases, but its involvement in inflammatory skin disorders is poorly known.

OBJECTIVES

To investigate the role of IL-26 in hidradenitis suppurativa (HS), through its involvement in antimicrobial activity.

METHODS

IL-26 was assessed in patients with HS through gene expression and protein analysis at skin and circulating levels. Ex vivo HS organ skin cultures, together with IL-26 antibody treatment, were performed to determine the IL-26 activity. Peripheral blood mononuclear cells (PBMCs) from patients with HS and healthy controls were either silenced or not with IL-26 small interfering (si)RNA in order to measure its antimicrobial, cytotoxic and phagocytic activities against Staphylococcus aureus.

RESULTS

Firstly, we observed that IL-26 is able to modulate the proinflammatory response at the immune cell level. IL-26 was increased in the plasma of patients with HS compared with healthy controls. Subsequently, we explored the bactericidal, cytotoxic and phagocytic activities of PBMCs against S. aureus in patients with HS and healthy controls. These activities were lower in patients with HS than in controls. Remarkably, the killing activities were reduced when healthy control PBMCs were transfected with IL-26 siRNA. However, the transfection did not affect the killing activity of HS PBMCs, supporting the idea that IL-26 lacks efficacy in HS.

CONCLUSIONS

Our findings suggest that infection susceptibility in HS might be related to IL-26. Although the role of bacteria remains controversial in HS, this paper supports that there is a defect of antimicrobial response in these patients. What's already known about this topic? Interleukin (IL)-26 is a T helper 17 cytokine described as an antimicrobial and proinflammatory mediator. IL-26 has been reported in immune-mediated inflammatory diseases, but its involvement in inflammatory skin disorders remains unclear. Hidradenitis suppurativa (HS) is a chronic inflammatory skin disorder characterized by deficiency of IL-20 and IL-22 (a close homologue of IL-26), which causes antimicrobial peptide pauperization leading to severe and recurrent skin infections. What does this study add? IL-26 plasma levels are higher in patients with HS than in healthy control individuals. The antimicrobial activity of IL-26 might be ineffective in patients with HS. What is the translational message? Cutaneous antimicrobial incompetence in HS could be related to IL-26.

Expression of IL-26 predicts prognosis of patients with hepatocellular carcinoma after surgical resection

BACKGROUND

There is no data regarding prognostic impact of interleukin (IL)-26 on outcomes of patients with hepatocellular carcinoma (HCC). The present study aimed to evaluate the prognostic impact of IL-26 on HCC patients undergoing liver resection.

METHODS

From 2003 to 2008, 122 patients with HCC who received surgical curative resection were enrolled. Patients were stratified into IL-26-upper and -lower groups according to the median expression level from immunohistochemical staining of resected specimens. Prognostic impact of IL-26 was estimated using Kaplan-Meier curves. Univariate and multivariate analyses were performed to evaluate time-dependent prognostic impact and independency of IL-26. Demographic and clinical factors that were associated with IL-26 were comprehensively identified.

RESULTS

Prognosis of the patients with high level of IL-26 revealed to be significantly unfavorable in both cumulative recurrence-free survival (P < 0.001) and overall survival (P = 0.002). Upper expression of IL-26 (HR: 1.643; 95% CI: 1.021 to 2.644; P = 0.041) and microvascular invasion (HR: 3.303; 95% CI: 1.255 to 8.696; P = 0.016) were identified as significant independent prognostic factors for overall survival in the multivariable analysis.

CONCLUSIONS

IL-26 is a novel prognostic factor for HCC after resection. Evaluation of IL-26 expression may be potentially valuable in clinical therapy when planning individualized follow-up schedule and evaluating candidates for prophylactic adjuvant treatment to prevent recurrence.

The Effect of IL-26 on TNF-α-Induced CXCL8 Responses by Colonic Epithelial Cell Lines

Th17 cells of the intestine and colon can produce several important cytokines during mucosal inflammation. However, few studies have focused on the role of IL-26 in intestinal inflammations. Colonic epithelial cells express receptors for IL-26, and this cytokine has been shown to induce the HT-29 colonic epithelial cell line to produce the chemokine CXCL8. However, epithelial cells would function in a cytokine network environment during mucosal inflammation and any effect of IL-26 on colonic epithelial cell chemokine responses could be affected by the presence of other potent pro-inflammatory cytokines like TNF-α and IL-1. Therefore, we investigated the effect of IL-26 with TNF-α or IL-1 on colonic epithelial cell line secretion of CXCL8. IL-26 alone had no effect on HT-29 or DLD1 cell line CXCL8 secretion. Yet, IL-26 was found to significantly enhance TNF-α-induced, but not IL-1-induced, CXCL8 secretion, but only at high levels of TNF-α. Similar results were seen with DLD1 cells. IL-26 did not enhance TNF-α-induced CXCL8 mRNA levels and did not affect TNF-α-induced IκBα phosphorylation or degradation. However, signaling through ERK and p38 MAPK were determined to be involved in the enhancing effect of IL-26 on the TNF-α-induced CXCL8 secretion, perhaps through known post-translational effects. These results suggest that the role of IL-26 in intestinal inflammation may be limited to enhancing CXCL8 secretion in the presence high levels of TNF-α, such as may occur in inflammatory bowel disease. Abbreviations: DMEM, Dulbecco's Modified Eagle's Medium; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IBD, inflammatory bowel disease; IL, interleukin; ITS, insulin, transferrin, selenium; TBS, Tris buffered saline; TNF, tumor necrosis factor.

IL-26, a Cytokine With Roles in Extracellular DNA-Induced Inflammation and Microbial Defense

Interleukin 26 (IL-26) is the most recently identified member of the IL-20 cytokine subfamily, and is a novel mediator of inflammation overexpressed in activated or transformed T cells. Novel properties have recently been assigned to IL-26, owing to its non-conventional cationic, and amphipathic features. IL-26 binds to DNA released from damaged cells and, as a carrier molecule for extracellular DNA, links DNA to inflammation. This observation suggests that IL-26 may act both as a driver and an effector of inflammation, leading to the establishment of a deleterious amplification loop and, ultimately, sustained inflammation. Thus, IL-26 emerges as an important mediator in local immunity/inflammation. The dysregulated expression and extracellular DNA carrier capacity of IL-26 may have profound consequences for the chronicity of inflammation. IL-26 also exhibits direct antimicrobial properties. This review summarizes recent advances on the biology of IL-26 and discusses its roles as a novel kinocidin.

The Interleukin-20 Cytokines in Intestinal Diseases

Autoimmune/inflammatory intestinal diseases, such as Crohn’s disease and ulcerative colitis, infectious gastrointestinal diseases, and gastrointestinal cancers, such as colorectal cancer, are worldwide a significant health problem. Intercellular communication and direct contact with the environment as the microbiota colonizes the gastrointestinal surface facilitates these diseases. Cytokines mediate the intercellular communication to maintain the equilibrium between host and environment and to regulate immune responses. One cytokine family that exchange information between immune cells and epithelial cells is the IL-20 cytokine family which includes the cytokines IL-19, IL-20, IL-22, IL-24, and IL-26. These cytokines share common receptor subunits and signaling pathways. IL-22 is the most intensively studied cytokine within this family in contexts of gastrointestinal disease, but the importance of other family members is more and more appreciated. In this review, the potential function of IL-20 cytokines concerning gastrointestinal conditions is discussed.

RETRACTED: Anti-angiogenic effect of Interleukin-26 in oxygen-induced retinopathy mice via inhibiting NFATc1-VEGF pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of authors. The Journal received an expression of concern from a reader, which noted that: “The problem is that there is no IL-26 gene in the mouse. They claim they bought the KO mouse and the mouse IL-26 protein but given that there is no mouse IL-26 gene, a purchase is not possible and in fact no such reagents are available. Furthermore they do reference and anti-IL-26 antibody but the spec sheet clearly states that it is only reactive with the human protein…., the Enzo Life Sciences online catalog does not have a listing for recombinant IL-26 of any kind.” The authors apologize for their mistakes and have asked to retract the article.