Cytokine and anti-cytokine therapies in prevention or treatment of fibrosis in IBD

CC group of chemokines and associated gene expression of transcription factors: Deciphering immuno-pathogenetic aspect of oral submucous fibrosis

BACKGROUND

Oral submucous fibrosis (OSMF) is a chronic disease with significantly increasing malignant transformation rate. To date the pathogenesis of OSMF has been considered to be associated with areca nut constituents and their action on fibroblasts. However, fibrosis is also associated with immunological factors such as chemokines. In-depth analysis of such factors is the need of the hour in OSMF to better understand the pathogenesis so that effective therapeutic strategies can be developed in the future.

MATERIALS AND METHOD

Clinically diagnosed cases of OSMF (n=21) and healthy individuals (n=10) were enrolled in the present study. Chemokines such as CCL2, CCL3, CCL4, CCL5, CCL11, CCL17, CCL28, CXCL1, CXCL5, CXCL8, CXCL9, CXCL10, and CXCL11 were assessed using the chemokine bead array in conjunction with the flow cytometry, along with real-time PCR (RT-PCR). The transcription factors CREB, NF-κB and NFAT5 were also studied for their expressions. The analysis of pg/ml (picogram/milliliter) values was done by using LEGENDplex™ Data Analysis Software.

RESULTS

The results obtained demonstrated early phase transient increase in CXCL-11, CCL20, CXCL9, CCL3, CCL2, CXCL10 and CXCL8. However, the expression of CCL3, CXCL10 and CXCL8 was higher in the late stage as compared to the early stage. The relative gene expression of CREB, NF-κB, NFAT5 were upregulated in the late stage of OSMF when compared to normal.

CONCLUSION

Distinctive sets of chemokine expression during the early and late stages of OSMF suggest a unique pattern of disease progression playing an important role in the pathogenesis.

Role of Serotonin in the Maintenance of Inflammatory State in Crohn’s Disease

Crohn’s disease (CD) is a chronic intestinal inflammation considered to be a major entity of inflammatory bowel diseases (IBDs), affecting different segments of the whole gastrointestinal tract. Peripheral serotonin (5-HT), a bioactive amine predominantly produced by gut enterochromaffin cells (ECs), is crucial in gastrointestinal functions, including motility, sensitivity, secretion, and the inflammatory response. These actions are mediated by a large family of serotonin receptors and specialized serotonin transporter (SERT) located on a variety of cell types in the gut. Several studies indicate that intestinal 5-HT signaling is altered in patients with inflammatory bowel disease. Paraformaldehyde-fixed intestinal tissues, obtained from fifteen patients with Crohn’s disease were analyzed by immunostaining for serotonin, Langerin/CD207, and alpha-Smooth Muscle Actin (α-SMA). As controls, unaffected (normal) intestinal specimens of seven individuals were investigated. This study aimed to show the expression of serotonin in dendritic cells (DCs) and myofibroblast which have been characterized with Langerin/CD207 and α-SMA, respectively; furthermore, for the first time, we have found the presence of serotonin in goblet cells. Our results show the correlation between different types of intestinal cells in the maintenance of the inflammatory state in CD linked to the recall of myofibroblasts.

Attenuation of Dupuytren's fibrosis via targeting of the STAT1 modulated IL-13Rα1 response

Fibrotic disorders represent common complex disease pathologies that are therapeutically challenging. Inflammation is associated with numerous fibrotic pathogeneses; however, its role in the multifaceted mechanisms of fibrosis remains unclear. IL-13 is implicated in aberrant responses involved in fibrotic disease, and we aimed to understand its role in the inflammatory processes of a common fibrotic disorder, Dupuytren's disease. We demonstrated T-cells produced IFN-g, which induced IL-13 secretion from mast cells and up-regulated IL-13Ra1 on fibroblasts, rendering them more reactive to IL-13. Consequently, diseased myofibroblasts demonstrated enhanced fibroproliferative effects upon IL-13 stimulation. We established IFN-g and IL-13 responses involved STAT dependent pathways, and STAT targeting (tofacitinib) could inhibit IL-13 production from mast cells, IL-13Ra1 up-regulation in fibroblasts and fibroproliferative effects of IL-13 on diseased myofibroblasts. Accordingly, utilizing Dupuytren's as an accessible human model of fibrosis, we propose targeting STAT pathways may offer previously unidentified therapeutic approaches in the management of fibrotic disease.

Cytokine Receptor Profiling in Human Colonic Subepithelial Myofibroblasts: A Differential Effect of Th Polarization-Associated Cytokines in Intestinal Fibrosis

BACKGROUND

Colonic subepithelial myofibroblasts (cSEMFs) are mesenchymal cells with a pivotal role in the pathophysiology of Crohn's disease (CD) fibrosis. Here, we demonstrate for the first time a complete expression mapping of cytokine receptors, implicated in inflammatory bowel diseases, in primary human cSEMFs and how pro-inflammatory cytokines regulate this expression. Furthermore, we show the effect of Th1-, Th2-, Th17- and Treg-related cytokines on a fibrosis-related phenotype of cSEMFs.

METHODS

Colonic subepithelial myofibroblasts were isolated from healthy individuals' colonic biopsies. Interleukin (IL)-1α- and/or tumor necrosis factor (TNF)-α-induced mRNA and protein expression of cytokine receptors was assayed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunofluorescence, respectively. Th-related cytokine effects on mRNA and protein profibrotic factor expression were analyzed by qRT-PCR and/or colorimetric assays and on the wound-healing capacity of cSEMFs by scratch test.

RESULTS

In cSEMFs, we observed basal cytokine receptor expression, which was modified by IL-1α and TNF-α. Th1-related cytokines upregulated tissue factor (TF), collagen, fibronectin and matrix metalloproteinase (MMP)-1 and downregulated α-smooth muscle actin (α-SMA), MMP-9, and wound healing rate. Th2-related cytokines upregulated collagen, TF, α-SMA, MMP-1, and wound healing rate and downregulated fibronectin and MMP-9. IL-17 and IL-23 upregulated fibronectin, and IL-22 downregulated TF. IL-17 and IL-22 decreased wound healing rate. Similar to TGF-β, IL-23 upregulated MMP-1, tissue inhibitor of metalloproteinases-1, collagen expression, and wound healing rates.

CONCLUSIONS

Our results suggest that cSEMFs have a central role in inflammation and fibrosis, as they express a great variety of Th-related cytokine receptors, making them responsive to pro-inflammatory cytokines, abundant in the inflamed mucosa of CD patients.

Chickpea supplementation prior to colitis onset reduces inflammation in dextran sodium sulfate-treated C57Bl/6 male mice

The potential for a chickpea-supplemented diet (rich in fermentable nondigestible carbohydrates and phenolic compounds) to modify the colonic microenvironment and attenuate the severity of acute colonic inflammation was investigated. C57Bl/6 male mice were fed a control basal diet or basal diet supplemented with 20% cooked chickpea flour for 3 weeks prior to acute colitis onset induced by 7-day exposure to dextran sodium sulfate (DSS; 2% w/v in drinking water) and colon and serum levels of inflammatory mediators were assessed. Despite an equal degree of DSS-induced epithelial barrier histological damage and clinical symptoms between dietary groups, biomarkers of the ensuing inflammatory response were attenuated by chickpea pre-feeding, including reduced colon tissue activation of nuclear factor kappa B and inflammatory cytokine production (tumor necrosis factor alpha and interleukin (IL)-18). Additionally, colon protein expression of anti-inflammatory (IL-10) and epithelial repair (IL-22 and IL-27) cytokines were increased by chickpea pre-feeding. Furthermore, during acute colitis, chickpea pre-feeding increased markers of enhanced colonic function, including Relmβ and IgA gene expression. Collectively, chickpea pre-feeding modulated the baseline function of the colonic microenvironment, whereby upon induction of acute colitis, the severity of the inflammatory response was attenuated.

CD16+ Macrophages Mediate Fibrosis in Inflammatory Bowel Disease

BACKGROUND AND AIMS

Fibrosis is a common complication of Crohn's disease [CD], and is related to dysregulated tissular repair following inflammation, in which macrophages play a central role. We have previously observed that STAT6-/- mice present delayed mucosal recovery after 2,4,6-trinitrobenzenesulfonic acid [TNBS]-induced colitis due to a deficiency in reparatory interleukin-4 [IL4]/STAT6-dependent M2 macrophages, which can be reverted by the exogenous transfer of this cell type. In the present study, we analyse the role of STAT6-dependent macrophages in intestinal fibrosis.

METHODS

Colitis was induced by weekly intra-rectal administration of TNBS [6 weeks] to STAT6-/- mice and wild-type [WT] animals. Colonic surgical resections were obtained from CD patients and from colon cancer patients.

RESULTS

Chronic colitis provoked a fibrogenic response in STAT6-/- mice, but not in WT animals. An accumulation of M2 macrophages, defined as CD206+ cells, was observed in WT mice, but not in STAT6-/- animals. Instead, the latter group showed an increase in CD16+ macrophages that correlated with the expression of fibrogenic markers. CD16+ macrophages were also increased in the damaged mucosa of Crohn's disease patients with stenotic or penetrating complications. Finally, administration of IL4-treated WT macrophages to STAT6-/- mice reduced TNBS-induced fibrosis.

CONCLUSIONS

Our study demonstrates that STAT6 deficiency dysregulates the macrophage response to inflammatory outbursts by increasing the presence of a population of CD16+ macrophages that seems to contribute to intestinal fibrosis.

Epithelial-mesenchymal transition in Crohn's disease

Crohn's disease (CD) is often accompanied by the complications of intestinal strictures and fistulas. These complications remain obstacles in CD treatment. In recent years, the importance of epithelial-mesenchymal transition in the pathogenesis of CD-associated fistulas and intestinal fibrosis has become apparent. Epithelial-mesenchymal transition refers to a dynamic change, wherein epithelial cells lose their polarity and adherence and acquire migratory function and fibroblast features. During formation of CD-associated fistulas, intestinal epithelial cells dislocate from the basement membrane and migrate to the lining of the fistula tracts, where they convert into transitional cells as a compensatory response under the insufficient wound healing condition. In CD-associated intestinal fibrosis, epithelial-mesenchymal transition may serve as a source of new fibroblasts and consequently lead to overproduction of extracellular matrix. In this review, we present current knowledge of epithelial-mesenchymal transition and its role in the pathogenesis of CD in order to highlight new therapy targets for the associated complications.

Navy and black bean supplementation attenuates colitis-associated inflammation and colonic epithelial damage

The enriched levels of nondigestible fermentable carbohydrates and phenolic compounds found in common beans can exert immunomodulatory effects within the colon that improve gut health and mitigate the severity of colitis-associated inflammatory pathology. Prior to acute colitis onset, C57Bl/6 mice were prefed isocaloric 20% cooked navy bean (NB) or black bean (BB) diets for 3 weeks and switched to control basal diet (BD) 24 h prior to colitis induction via 5-day exposure to dextran sodium sulfate (2% w/v in drinking water)+3 days of fresh water. The severity of the acute colitis phenotype was attenuated by bean prefeeding, evidenced by reduced colon tissue inflammatory transcription factor activation (NFκB, STAT3) and inflammatory mediator levels in the colon (IL-1β, IL-6, IL-18 and MCP-1) and serum (TNFα, IL-6, IL-1β, MCP-1) versus BD (P≤.05). Additionally, biomarkers of enhanced wound repair responses were increased by bean prefeeding including colon tissue protein levels of IL-22, IL-27 and activated (i.e., GTP-bound) Cdc42 and Rac1 versus BD (P≤.05). mRNA expressions of genes involved in normal colonic epithelial function and the promotion of epithelial barrier integrity, defense and/or restitution and wound closure including MUC1, RELMβ, IgA and REG3γ were all increased in NB and BB prefed mice versus BD (P≤.05). Collectively, bean supplementation prior to colitis induction (i.e., mimicking disease relapse) primes the colonic microenvironment to attenuate the severity of the colitis inflammatory phenotype and maintain aspects of epithelial barrier function.

DNA methylation regulated gene expression in organ fibrosis

DNA methylation is a major epigenetic mechanism to regulate gene expression. Epigenetic regulation, including DNA methylation, histone modifications and RNA interference, results in heritable changes in gene expression independent of alterations in DNA sequence. Epigenetic regulation often occurs in response to aging and environment stimuli, including exposures and diet. Studies have shown that DNA methylation is critical in the pathogenesis of fibrosis involving multiple organ systems, contributing to significant morbidity and mortality. Aberrant DNA methylation can silence or activate gene expression patterns that drive the fibrosis process. Fibrosis is a pathological wound healing process in response to chronic injury. It is characterized by excessive extracellular matrix production and accumulation, which eventually affects organ architecture and results in organ failure. Fibrosis can affect a wide range of organs, including the heart and lungs, and have limited therapeutic options. DNA methylation, like other epigenetic process, is reversible, therefore regarded as attractive therapeutic interventions. Although epigenetic mechanisms are highly interactive and often reinforcing, this review discusses DNA methylation-dependent mechanisms in the pathogenesis of organ fibrosis, with focus on cardiac and pulmonary fibrosis. We discuss specific pro- and anti-fibrotic genes and pathways regulated by DNA methylation in organ fibrosis; we further highlight the potential benefits and side-effects of epigenetic therapies in fibrotic disorders.

Toll-like receptors 2 and 4 modulate intestinal IL-10 differently in ileum and colon

Background

Inflammatory bowel diseases are consequence of an intestinal homeostasis breakdown in which innate immune dysregulation is implicated. Toll-like receptor (TLR)2 and TLR4 are immune recognition receptors expressed in the intestinal epithelium, the first physical-physiological barrier for microorganisms, to inform the host of the presence of Gram-positive and Gram-negative organisms. Interleukin (IL)-10 is an essential anti-inflammatory cytokine that contributes to maintenance of intestinal homeostasis.

Aim

Our main aim was to investigate intestinal IL-10 synthesis and release, and whether TLR2 and TLR4 are determinants of IL-10 expression in the intestinal tract.

Methods

We used Caco-2 cell line as an enterocyte-like cell model, and also ileum and colon from mice deficient in TLR2, TLR4 or TLR2/4 to test the involvement of TLR signaling.

Results

Intestinal epithelial cells are able to synthesize and release IL-10 and their expression is increased after TLR2 or TLR4 activation. IL-10 regulation seems to be tissue specific, with IL-10 expression in the ileum regulated by a compensation between TLR2 and TLR4 expression, whereas in the colon, TLR2 and TLR4 affect IL-10 expression independently.

Conclusions

Intestinal epithelial cells could release IL-10 in response to TLR activation, playing an intestinal tissue-dependent and critical intestinal immune role.

Significant contribution of TRPC6 channel-mediated Ca2+ influx to the pathogenesis of Crohn's disease fibrotic stenosis

Intestinal fibrosis is an intractable complication of Crohn's disease (CD), and, when occurring excessively, causes severe intestinal obstruction that often necessitates surgical resection. The fibrosis is characterized by an imbalance in the turnover of extracellular matrix (ECM) components, where intestinal fibroblasts/myofibroblasts play active roles in ECM production, fibrogenesis and tissue remodeling, which eventually leads to the formation of stenotic lesions. There is however a great paucity of knowledge about how intestinal fibrosis initiates and progresses, which hampers the development of effective pharmacotherapies against CD. Recently, we explored the potential implications of transient receptor potential (TRP) channels in the pathogenesis of intestinal fibrosis, since they are known to act as cellular stress sensors/transducers affecting intracellular Ca²⁺ homeostasis/dynamics, and are involved in a broad spectrum of cell pathophysiology including inflammation and tissue remodeling. In this review, we will place a particular emphasis on the intestinal fibroblast/myofibroblast TRPC6 channel to discuss its modulatory effects on fibrotic responses and therapeutic potential for anti-fibrotic treatment against CD-related stenosis.

Toward an antifibrotic therapy for inflammatory bowel disease

Fibrosis in inflammatory bowel disease (IBD) is a largely unresolved clinical problem. Despite recent advances in anti-inflammatory therapies over the last few decades, the occurrence of intestinal strictures in Crohn's disease patients has not significantly changed. No antifibrotic therapies are available. This journal supplement will address novel mechanisms of intestinal fibrosis, biomarker and imaging techniques and is intended to provide a roadmap toward antifibrotic therapies in IBD.