Interleukin-21 (IL-21) controls inflammatory pathways in the gut

The IL-21/IL-21R signaling axis regulates CD4+ T cell responsiveness to IL-12 to promote bacterial-induced colitis

IL-21/IL-21R signaling dysregulation is linked to multiple chronic intestinal inflammatory disorders in humans and animal models of human diseases. In addition to its critical requirement for the generation and development of germinal center B cells, IL-21/IL-21R signaling can also regulate the effector functions of a variety of T cell subsets. The antibody-mediated abrogation of IL-21/IL-21R signaling led to the impaired expression of IFN-γ by mucosal CD4+ T cells from human subjects with colitis, suggesting an IL-21/IL-21R-triggered positive feedback loop of the TH1 immune response in the colon. Despite recent advances in our understanding of the mechanisms underpinning the regulation of pro-inflammatory immune responses by the IL-21/IL-21R signaling axis, it remains unclear how this pathway or its downstream molecules contribute to inflammation during bacterial-induced colitis. This study found that IL-21 enhances the surface expression of IL-12Rβ2, but not IL-12Rβ1, in CD4+ T cells, leading to TH1 differentiation and stability. Consistently, these findings also point to an indispensable role of the IL-12Rβ2 signaling axis in promoting pro-inflammatory immune responses during Citrobacter rodentium-induced colitis. Genetic deletion of the IL-12Rβ2 signaling pathway led to the attenuation of C. rodentium-induced colitis in vivo. The genetic deletion of the IL-12Rβ2 signaling pathway did not alter the host's ability to respond adequately to C. rodentium infection or the ability of Il12rb2-/- mice to express antigen-specific cytokines (IFN-γ, IL-17A). IL-21 is a pleiotropic cytokine exerting a wide range of immunomodulatory functions in multiple tissues, and its direct targeting may result in undesirable off-target consequences. These findings highlight the possibility for targeted manipulations of signaling cascades downstream of main regulators of pro-inflammatory responses to control invading pathogens while preserving the integrity of host immune responses. A better understanding of the novel mechanisms by which IL-21/IL-21R signaling regulates bacterial-induced colitis will provide insights into the development of new therapeutic and preventive strategies to harness IL-21/IL-21R signaling or its downstream molecules to treat infectious colitis.

Eugenol Alleviates Dextran Sulfate Sodium-Induced Colitis Independent of Intestinal Microbiota in Mice

The present study investigated the effect of eugenol (EUG) on dextran sulfate sodium (DSS)-induced colitis and explored the underlying mechanisms. C57BL/6 mice were intragastrically administered normal saline or EUG (20 mg/kg body weight) for 17 days, and colitis was induced by using 3% DSS from day 7. The results showed that EUG increased the body weight and reduced the disease activity index score and colon pathological scores in DSS-treated mice (P < 0.05). Further, EUG preserved the proinflammatory cytokines (interleukin (IL)-6, -12, -21, and -23), lowered (P < 0.05) colonic malondialdehyde (MDA), uncoupling protein 2 (UCP2) expression and p65 phosphorylation, and activated (P < 0.05) colonic kelch-like ECH-associated protein 1 and nuclear factor (erythroid-derived 2)-like 2 expressions but did not affect the intestinal microbiota in DSS-treated mice. Furthermore, EUG ameliorated colitis in antibiotic-treated mice, while fecal microbiota transplantation from EUG preadministered mice failed to ameliorate colitis. In conclusion, EUG could alleviate colitis by attenuating colonic inflammation and oxidative stress independent of intestinal microbiota.

Faecal cytokine profiling as a marker of intestinal inflammation in acutely decompensated cirrhosis

BACKGROUND & AIMS

Gut dysbiosis and inflammation perpetuate loss of gut barrier integrity (GBI) and pathological bacterial translocation (BT) in cirrhosis, contributing to infection risk. Little is known about gut inflammation in cirrhosis and how this differs in acute decompensation (AD). We developed a novel approach to characterise intestinal immunopathology by quantifying faecal cytokines (FCs) and GBI markers.

METHODS

Faeces and plasma were obtained from patients with stable cirrhosis (SC; n = 16), AD (n = 47), and healthy controls (HCs; n = 31). A panel of 15 cytokines and GBI markers, including intestinal fatty-acid-binding protein-2 (FABP2), d-lactate, and faecal calprotectin (FCAL), were quantified by electrochemiluminescence/ELISA. Correlations between analytes and clinical metadata with univariate and multivariate analyses were performed.

RESULTS

Faecal (F) IL-1β, interferon gamma, tumour necrosis factor alpha, IL-21, IL-17A/F, and IL-22 were significantly elevated in AD vs. SC (q <0.01). F-IL-23 was significantly elevated in AD vs. HC (p = 0.0007). FABP2/d-lactate were significantly increased in faeces in AD vs. SC and AD vs. HC (p <0.0001) and in plasma (p = 0.0004; p = 0.011). F-FABP2 correlated most strongly with disease severity (Spearman's rho: Child-Pugh 0.466; p <0.0001; model for end-stage liver disease 0.488; p <0.0001). FCAL correlated with plasma IL-21, IL-1β, and IL-17F only and none of the faecal analytes. F-cytokines and F-GBI markers were more accurate than plasma in discriminating AD from SC.

CONCLUSIONS

FC profiling represents an innovative approach to investigating the localised intestinal cytokine micro-environment in cirrhosis. These data reveal that AD is associated with a highly inflamed and permeable gut barrier. FC profiles are very different from the classical innate-like features of systemic inflammation. There is non-specific upregulation of TH1/TH17 effector cytokines and those known to mediate intestinal barrier damage. This prevents mucosal healing in AD and further propagates BT and systemic inflammation.

LAY SUMMARY

The gut barrier is crucial in cirrhosis in preventing infection-causing bacteria that normally live in the gut from accessing the liver and other organs via the bloodstream. Herein, we characterised gut inflammation by measuring different markers in stool samples from patients at different stages of cirrhosis and comparing this to healthy people. These markers, when compared with equivalent markers usually measured in blood, were found to be very different in pattern and absolute levels, suggesting that there is significant gut inflammation in cirrhosis related to different immune system pathways to that seen outside of the gut. This provides new insights into gut-specific immune disturbances that predispose to complications of cirrhosis, and emphasises that a better understanding of the gut-liver axis is necessary to develop better targeted therapies.

Characterization and bioactivity of grass carp (Ctenopharyngodon idella) interleukin-21: Inducible production and involvement in inflammatory regulation

In mammals, interleukin 21 (IL-21) is a broad pleiotropic cytokine that plays critical roles in the development of several inflammatory and autoimmune diseases. In fish, functional information of Il-21 is limited, and its role in immune response is largely unknown. In the present study, we cloned a coding sequence of grass carp (Ctenopharyngodon idella) il21 gene (gcil21). To characterize the release patterns and biological activity of gcIl-21, we prepared recombinant gcIl-21 (rgcIl-21) and obtained the polyclonal antibody with gcIl-21 specificity. Western blotting analysis showed that in grass carp head kidney leukocytes (HKLs), gcIl-21 was undetected in culture supernatant of untreated cells but drastically induced by heat-killed Aeromonas hydrophila (A. hydrophila), uncovering the release features of gcIl-21 and its possible involvement in immune response. Subsequent functional experiments revealed that rgcIl-21 did not affect the mRNA expression of grass carp il1b and tgfb, but induced a strong expression of grass carp il10, and to a lesser extent of grass carp tnfa in HKLs, suggesting a dominant effect of gcIl-21 in modulating Il-10 signaling as seen in rainbow trout and mammals. Furthermore, in vivo studies showed that intraperitoneal injection of rgcIl-21 was able to increase the survival rate of grass carp infected with live A. hydrophila, and reduce the pathological responses caused by the same pathogenic bacteria in head kidney and intestine. Taken together, these results for the first time revealed the close relationship of fish Il-21 production and function with inflammatory responses, and highlighted its anti-bacterial and anti-inflammatory ability, thereby providing a new insight into host defense mechanisms in fish.

Curcumin and Intestinal Inflammatory Diseases: Molecular Mechanisms of Protection

Intestinal inflammatory diseases, such as Crohn’s disease, ulcerative colitis, and necrotizing enterocolitis, are becoming increasingly prevalent. While knowledge of the pathogenesis of these related diseases is currently incomplete, each of these conditions is thought to involve a dysfunctional, or overstated, host immunological response to both bacteria and dietary antigens, resulting in unchecked intestinal inflammation and, often, alterations in the intestinal microbiome. This inflammation can result in an impaired intestinal barrier allowing for bacterial translocation, potentially resulting in systemic inflammation and, in severe cases, sepsis. Chronic inflammation of this nature, in the case of inflammatory bowel disease, can even spur cancer growth in the longer-term. Recent research has indicated certain natural products with anti-inflammatory properties, such as curcumin, can help tame the inflammation involved in intestinal inflammatory diseases, thus improving intestinal barrier function, and potentially, clinical outcomes. In this review, we explore the potential therapeutic properties of curcumin on intestinal inflammatory diseases, including its antimicrobial and immunomodulatory properties, as well as its potential to alter the intestinal microbiome. Curcumin may play a significant role in intestinal inflammatory disease treatment in the future, particularly as an adjuvant therapy.

Biological activities of interleukin (IL)-21 in human monocytes and macrophages

The biological roles of interleukin (IL)-21 in human monocytes and macrophages have been neglected. We previously demonstrated that IL-21 induce phagocytosis and established that Syk is a new molecular target of IL-21. Herein, we found that IL-21 is not chemoattractant for immature THP-1 and primary monocytes but can increase the capacity of THP-1 cells (not primary monocytes) to adhere onto a cell substratum by a Syk-dependent mechanism without altering the expression of a panel of cell surface molecules. Unlike THP- 1 and monocytes, IL-21 can increase metalloproteinase (MMP)-9 secretion and activity in monocyte-derived macrophages (HMDM), as assessed by western blot and zymography experiments, respectively. We reported that IL-21 did not increase the production of IL-6 and the chemokines MIP-1α and GRO-α in HMDM. Therefore, IL-21 can increase functions other that phagocytosis, but this cytokine does not have a large spectrum of biological activities in monocytes and macrophages.

Protective Role of Coxsackie-Adenovirus Receptor in the Pathogenesis of Inflammatory Bowel Diseases

AIM

To investigate the role of Coxsackie-adenovirus receptor (CAR) in inflammatory bowel disease (IBD).

BACKGROUND

CAR, a type I transmembrane protein with functions in virus attachment, has been shown to be associated with epithelial tight junctions (TJs) and mediates cell adhesion, implying its potential roles in the pathogenesis of IBD.

METHODS AND MATERIALS

To determine the effect of CAR in IBD using QPCR and Western blotting to determine the expression of CAD in TNF-α induced NCM460 and SW480 cells and IBD tissues compared to control groups. Furthermore, TJs dysregulation, FITC-Dextran permeability assay, qRT-PCR, Western blot, and IF assessed the permeability in CAR overexpressed cells treated with TNF-α. HE, qRT-PCR, Western blot, and IHC assay were used to assess the CAR overexpressed cells whether they have the effect to cure DSS induced ulcerative colitis rat model in vivo.

RESULT

We found CAR levels in human colon cell lines are significantly downregulated under the treatment of tumor necrosis factor-alpha (TNF-α). Furthermore, overexpression of CAR markedly prevented TNF-α induced inflammatory response, TJs dysregulation, and permeability disruption (FITC-Dextran permeability assay) in cells. Consistent with these findings in vitro, we found that CAR overexpression could suppress gut inflammation, attenuate the downregulation of TJ protein ZO-1 and Occludin, and limit the induction of barrier permeability in a DSS induced ulcerative colitis rat model in vivo. Together, our findings strongly suggest that CAR could protect tight junctions and has an anti-inflammatory effect during the pathogenesis of IBD. Thus CAR may serve as a therapeutic target for the diagnosis and treatment of IBD.

Cellular and Molecular Mediators of Intestinal Fibrosis

Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.

Cellular and Molecular Mediators of Intestinal Fibrosis

Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.

Differential expression of Th17 cytokines in the colon of rats in different inflammatory periods of Crohn's disease

AIM: To observe the intestinal inflammatory status and the expression of interleukin (IL)-6, IL-17A, IL-21, and retinoid-related orphan nuclear receptor γt (RORγt) secreted by Th17 cells in colon tissues of rats with trinitro-benzene-sulfonic acid (TNBS) induced Crohn's disease.

METHODS: Thirty male rats were randomly divided into a normal control group and 1-, 2-, 3- and 4-wk model groups. Morphological observation and HE staining were used to assess the degree of damage to the colonic mucosa. Fluorescence quantitative PCR, immunohistochemical method and other techniques were used to observe the expression of RORγt and IL-17A in rat colonic mucosa, and ELISA method was used to detect the contents of IL-6 and IL-21 in serum.

RESULTS: The level of IL-17A mRNA in rat colon decreased at the first induction with TNBS, but the levels of IL-17A mRNA and protein obviously increased (P < 0.05) at 3 wk and reached the highest after the fourth induction. The expression of RORγt protein gradually increased after induction (P < 0.05), and reached the highest at the fourth induction (P < 0.05). The contents of IL-6 and IL-21 in serum obviously increased from the first week (P < 0.01), reaching the highest at the fourth week. The colon general morphological score and tissue damage score of model rats obviously increased (P < 0.01).

CONCLUSION: During the process of Crohn's disease induced with TNBS, the contents of IL-6, IL-17A, IL-21, and RORγt secreted by Th17 cells gradually increased and the degree of colonic inflammation gradually exacerbated.

Elevated expression of interleukin-21 and its correlation to T-cell subpopulation in patients with ulcerative colitis

Objective

To investigate the expression of interleukin-21 (IL-21) and its correlation to T-cell subpopulation including Th1, Tc1 and Th17 cells in Ulcerative colitis (UC).

Material and methods

We examined the expression of IL-21, IL-17 and IFN-γ in UC patients and controls by enzyme-linked immunosorbent assay (ELISA) and flow cytometry.

Results

We found that IL-21 was expressed on CD3⁺CD8^-T cells by flow cytometry. Plasma IL-21 level and the percentage of CD3⁺CD8^-IL-21⁺ T cells were significantly elevated in UC patients compared to controls. The percentage of CD3⁺CD8^-IL-17⁺ T (Th17), CD3⁺CD8^-IFN-γ⁺ T (Th1) and CD3⁺CD8⁺ IFN-γ⁺ T (Tc1) cells was also significantly increased in UC patients. Moreover, we found a significant positive correlation between CD3⁺CD8^-IL-21⁺T cells and Th17 cells.

Conclusions

Elevated IL-21 and its positive correlation to Th17 cells may play a role in the pathogenesis of UC.

Interleukin‑21 promotes the development of ulcerative colitis and regulates the proliferation and secretion of follicular T helper cells in the colitides microenvironment

Patients with ulcerative colitis (UC) are at increased risk of developing colitis‑associated colon cancer. Previous studies have indicated that interleukin (IL)‑21, which is predominantly secreted by follicular T helper (Tfh) cells, is overproduced in inflammatory bowel diseases. In order to investigate the role of IL‑21 in UC and the association between IL‑21 and Tfh cells, the number of Tfh cells and the level of IL‑21 were investigated in colonic tissues from UC patients and wild‑type (WT) mice, which were induced by dextran sulphate sodium (DSS). High Tfh cell counts and levels of IL‑21 were observed in UC patients and WT mice with DSS‑induced colitis. Subsequent comparison of the mucosal damage and expression of Tfh‑associated cytokines in the WT mice and IL‑21 knockout (IL‑21KO) mice following DSS administration, revealed that IL‑21KO mice were largely protected against colitis and exhibited reduced infiltration of Tfh cells, as well as decreased production of Tfh‑associated cytokines. The present study also found that IL‑21 was necessary for the proliferation and secretion of Tfh cells in vitro. In addition, neutralization of IL‑21 in DSS‑administered WT mice using anti‑IL‑21 reduced the number of Tfh cells and the level of mucosal damage. Administration of a neutralizing IL‑21 antibody decreased the colonic infiltration of Tfh cells and reduced damage to the mucosa. These results indicated that Tfh cells are important in UC and that its effector molecule, IL‑21, is not only a critical regulator of inflammation, but also regulates the proliferation and response of Tfh cells in the colitis microenvironment.

Changes of the cytokine profile in inflammatory bowel diseases

Cytokines are indispensable signals of the mucosa-associated immune system for maintaining normal gut homeostasis. An imbalance of their profile in favour of inflammation initiation may lead to disease states, such as that is observed in inflammatory bowel diseases (IBD). Although Crohn's disease (CD) is often described as a prototype of T-helper 1-type diseases, and ulcerative colitis (UC) is traditionally viewed as a T-helper 2-mediated condition, the classic paradigm, which categorises cytokines into pro- and anti-inflammatory groups, has recently been changed. The inflammation regulatory pathways may not be mutually exclusive as individual cytokines can have diverse and even opposing functions in various clinical and immunological settings. None the less there are many common immunological responses in IBD that are mediated by cytokines. Although they regulate and influence the development, course and recurrence of the inflammatory process, the concrete pathogenic role of these small signaling molecules is sometimes not unambiguous in the subtypes of the disease. Our aim is to review the current information about pro- and anti-inflammatory effects of traditionally studied and recently discovered cytokines in the pathogenesis of UC and CD. The better understanding of their production and functional activity may lead to the development of new therapeutic modalities.

Cellular and molecular mechanisms of intestinal fibrosis

Fibrosis is a chronic and progressive process characterized by an excessive accumulation of extracellular matrix (ECM) leading to stiffening and/or scarring of the involved tissue. Intestinal fibrosis may develop in several different enteropathies, including inflammatory bowel disease. It develops through complex cell, extracellular matrix, cytokine and growth factor interactions. Distinct cell types are involved in intestinal fibrosis, such as resident mesenchymal cells (fibroblasts, myofibroblasts and smooth muscle cells) but also ECM-producing cells derived from epithelial and endothelial cells (through a process termed epithelial- and endothelial-mesenchymal transition), stellate cells, pericytes, local or bone marrow-derived stem cells. The most important soluble factors that regulate the activation of these cells include cytokines, chemokines, growth factors, components of the renin-angiotensin system, angiogenic factors, peroxisome proliferator-activated receptors, mammalian target of rapamycin, and products of oxidative stress. It soon becomes clear that although inflammation is responsible for triggering the onset of the fibrotic process, it only plays a minor role in the progression of this condition, as fibrosis may advance in a self-perpetuating fashion. Definition of the cellular and molecular mechanisms involved in intestinal fibrosis may provide the key to developing new therapeutic approaches.

Generation and characterization of human anti-human IL-21 neutralizing monoclonal antibodies

Interleukin-21 (IL-21) is a type I four-helical bundle cytokine that exerts a variety of significant effects on many hematopoietic cells, including T and B lymphocytes and natural killer cells. IL-21 is produced predominantly by CD4+ T cells and natural killer T cells and, when aberrantly overexpressed, appears to play important roles in a wide variety of autoimmune disorders. To generate potential therapeutic reagents capable of inhibiting IL-21 for clinical use, we immunized human immunoglobulin transgenic mice with IL-21 and then identified and cloned a panel of human anti-human IL-21 binding monoclonal antibodies. IL-21 neutralizing and IL-21-binding, non-neutralizing antibodies were assigned to distinct epitope "bins" based on surface plasmon resonance competition studies. The most potent neutralizing antibodies had extremely high (sub pM) affinity for IL-21 and were able to block IL-21 activity in various biological assays using either an IL-21R-transfected pre-B-cell line or primary human B cells, and their neutralizing activity was, in some cases, superior to that of a soluble form of the high affinity heterodimeric IL-21 receptor. Characterization of this panel of IL-21 antibodies provided the basis for the selection of a therapeutic candidate antibody capable of inhibiting IL-21 activity for the treatment of autoimmune and inflammatory diseases.

Expression of cluster of differentiation antigen-14 in intestinal mucosa of patients with inflammatory bowel disease and its implication

AIM: To investigate the expression of CD14 in intestinal mucosa of patients with inflammatory bowel disease and its relationship with the disease.

METHODS: Specimens from 25 cases of ulcerative colitis (UC) and 15 Crohn's disease (CD) and 20 controls were studied by immunohistochemical staining. The clinical diagnosis of inflammatory bowel disease was confirmed according to the routine radiologic, endoscopic and histologic criteria. All controls had normal colonoscopy, and the mucosal biopsies were histologically normal.

RESULTS: There was expression of CD14 in lamina propria. Percent of positive cells in intestinal mucosa in ulcerative colitis was higher than that in Crohn's disease, but without significant difference (P > 0.05). There was significant difference between ulcerative colitis and controls (t = 4.404, P < 0.01). Difference was also significant between Crohn's disease and controls (t = 3.324, P < 0.01). CD14 was positively related to the disease activity index. There was significant difference among slight, moderate and severe UC (F = 56.709, P < 0.01) and as well as among the slight, moderate and severe CD (F = 12.880, P < 0.01).

CONCLUSION: CD14 may be involved in the pathogenesis of inflammatory bowel disease, and its intensity reflects the activity of the disease.

Detecting shared pathogenesis from the shared genetics of immune-related diseases

Recent genetic studies have revealed shared immunological mechanisms in several immune-related disorders that further our understanding of the development and concomitance of these diseases. Our Review focuses on these shared aspects, using the novel findings of recently performed genome-wide association studies and non-synonymous SNP scans as a starting point. We discuss how identifying new genes that are associated with more than one autoimmune or chronic inflammatory disorder could explain the genetic basis of the shared pathogenesis of immune-related diseases. This analysis helps to highlight the key molecular pathways that are involved in these disorders and the potential roles of novel genes in immune-related diseases.

Limited effects of dietary curcumin on Th-1 driven colitis in IL-10 deficient mice suggest an IL-10-dependent mechanism of protection

Curcumin (diferulolylmethane) demonstrates profound anti-inflammatory effects in intestinal epithelial cells (IEC) and in immune cells in vitro and exhibits a protective role in rodent models of chemically induced colitis, with its presumed primary mechanism of action via inhibition of NF-kappaB. Although it has been demonstrated effective in reducing relapse rate in ulcerative colitis patients, curcumin's effectiveness in Crohn's disease (CD) or in Th-1/Th-17 mediated immune models of CD has not been evaluated. Therefore, we investigated the effects of dietary curcumin (0.1-1%) on the development of colitis, immune activation, and in vivo NF-kappaB activity in germ-free IL-10(-/-) or IL-10(-/-);NF-kappaB(EGFP) mice colonized with specific pathogen-free microflora. Proximal and distal colon morphology showed a mild protective effect of curcumin only at 0.1%. Colonic IFN-gamma and IL-12/23p40 mRNA expression followed similar pattern ( approximately 50% inhibition at 0.1%). Secretion of IL-12/23p40 and IFN-gamma by colonic explants and mesenteric lymph node cells was elevated in IL-10(-/-) mice and was not decreased by dietary curcumin. Surprisingly, activation of NF-kappaB in IL-10(-/-) mice (phospho-NF-kappaBp65) or in IL-10(-/-);NF-kappaB(EGFP) mice (whole organ or confocal imaging) was not noticeably inhibited by curcumin. Furthermore, we demonstrate that IL-10 and curcumin act synergistically to downregulate NF-kappaB activity in IEC and IL-12/23p40 production by splenocytes and dendritic cells. In conclusion, curcumin demonstrates limited effectiveness on Th-1 mediated colitis in IL-10(-/-) mice, with moderately improved colonic morphology, but with no significant effect on pathogenic T cell responses and in situ NF-kappaB activity. In vitro studies suggest that the protective effects of curcumin are IL-10 dependent.

Role of cytokines in inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn’s disease (CD) and ulcerative colitis (UC), represents a group of chronic disorders characterized by inflammation of the gastrointestinal tract, typically with a relapsing and remitting clinical course. Mucosal macrophages play an important role in the mucosal immune system, and an increase in the number of newly recruited monocytes and activated macrophages has been noted in the inflamed gut of patients with IBD. Activated macrophages are thought to be major contributors to the production of inflammatory cytokines in the gut, and imbalance of cytokines is contributing to the pathogenesis of IBD. The intestinal inflammation in IBD is controlled by a complex interplay of innate and adaptive immune mechanisms. Cytokines play a key role in IBD that determine T cell differentiation of Th1, Th2, T regulatory and newly described Th17 cells. Cytokines levels in time and space orchestrate the development, recurrence and exacerbation of the inflammatory process in IBD. Therefore, several cytokine therapies have been developed and tested for the treatment of IBD patients.

Advances in biological function of interleukin-21 and inflammatory bowel disease

Interleukin-21 (IL-21) is a recently discovered cytokine. Once combined with its receptor, IL-21 can regulate B cell proliferation, promote proliferation and differentiation of T cells and NK cells and enhance killing activity of NK cells. Inflammatory bowel disease (IBD) is a kind of autoimmune disease. Its pathogenesis is not clear yet and many factors may participate in it. Immunological derangement plays a significant role in IBD development which involves alteration of several cytokines. IL-21 is just one of them. This article reviewed IL-21 and its relationship with IBD.