STAT6 deficiency ameliorates severity of oxazolone colitis by decreasing expression of claudin-2 and Th2-inducing cytokines

A comprehensive immunobiology review of IBD: With a specific glance to Th22 lymphocytes development, biology, function, and role in IBD

The two primary forms of inflammatory disorders of the small intestine andcolon that make up inflammatory bowel disease (IBD) are ulcerative colitis (UC) and Crohn's disease (CD). While ulcerative colitis primarily affects the colon and the rectum, CD affects the small and large intestines, as well as the esophagus,mouth, anus, andstomach. Although the etiology of IBD is not completely clear, and there are many unknowns about it, the development, progression, and recurrence of IBD are significantly influenced by the activity of immune system cells, particularly lymphocytes, given that the disease is primarily caused by the immune system stimulation and activation against gastrointestinal (GI) tract components due to the inflammation caused by environmental factors such as viral or bacterial infections, etc. in genetically predisposed individuals. Maintaining homeostasis and the integrity of the mucosal barrier are critical in stopping the development of IBD. Specific immune system cells and the quantity of secretory mucus and microbiome are vital in maintaining this stability. Th22 cells are helper T lymphocyte subtypes that are particularly important for maintaining the integrity and equilibrium of the mucosal barrier. This review discusses the most recent research on these cells' biology, function, and evolution and their involvement in IBD.

Mirabegron, dependent on β3-adrenergic receptor, alleviates mercuric chloride-induced kidney injury by reversing the impact on the inflammatory network, M1/M2 macrophages, and claudin-2

The β3-adrenergic receptor (β3-AR) agonism mirabegron is used to treat overactive urinary bladder syndrome; however, its role against acute kidney injury (AKI) is not unveiled, hence, we aim to repurpose mirabegron in the treatment of mercuric chloride (HgCl2)-induced AKI. Rats were allocated into normal, normal + mirabegron, HgCl2 untreated, HgCl2 + mirabegron, and HgCl2 + the β3-AR blocker SR59230A + mirabegron. The latter increased the mRNA of β3-AR and miR-127 besides downregulating NF-κB p65 protein expression and the contents of its downstream targets iNOS, IL-4, -13, and -17 but increased that of IL-10 to attest its anti-inflammatory capacity. Besides, mirabegron downregulated the protein expression of STAT-6, PI3K, and ERK1/2, the downstream targets of the above cytokines. Additionally, it enhanced the transcription factor PPAR-α but turned off the harmful hub HNF-4α/HNF-1α and the lipid peroxide marker MDA. Mirabegron also downregulated the CD-163 protein expression, which besides the inhibited correlated cytokines of M1 (NF-κB p65, iNOS, IL-17) and M2 (IL-4, IL-13, CD163, STAT6, ERK1/2), inactivated the macrophage phenotypes. The crosstalk between these parameters was echoed in the maintenance of claudin-2, kidney function-related early (cystatin-C, KIM-1, NGAL), and late (creatinine, BUN) injury markers, besides recovering the microscopic structures. Nonetheless, the pre-administration of SR59230A has nullified the beneficial effects of mirabegron on the aforementioned parameters. Here we verified that mirabegron can berepurposedto treat HgCl2-induced AKI by activating the β3-AR. Mirabegron signified its effect by inhibiting inflammation, oxidative stress, and the activated M1/M2 macrophages, events that preserved the proximal tubular tight junction claudin-2 via the intersection of several trajectories.

Allergic Airway Inflammation Emerges from Gut Inflammation and Leakage in Mouse Model of Asthma

Asthma is an allergic airway inflammatory disease characterized by type 2 immune responses. Growing evidence suggests an association between allergic airways and intestinal diseases. However, the primary site of disease origin and initial mechanisms involved in the development of allergic airway inflammation (AAI) is not yet understood. Therefore, the initial contributing organs and mechanisms involved in the development of AAI are investigated using a mouse model of asthma. This study, without a local allergen challenge into the lungs, demonstrates a significant increase in intestinal inflammation with signature type-2 mediators including IL-4, IL-13, STAT6, eosinophils, and Th2 cells. In addition, gut leakage and mRNA expressions of gut leakage markers significantly increase in the intestine. Moreover, reduced mRNA expressions of tight junction proteins are observed in gut and interestingly, in lung tissues. Furthermore, in lung tissues, an increased pulmonary barrier permeability and IL-4 and IL-13 levels associated with significant increase of lipopolysaccharide-binding protein (LBP-gut leakage marker) and eosinophils are observed. However, with local allergen challenges into the lungs, these mechanisms are further enhanced in both gut and lungs. In conclusion, the primary gut originated inflammatory responses translocates into the lungs to orchestrate AAI in a mouse model of asthma.

Myrrh protects against IL-13-induced epithelial barrier breakdown in HT-29/B6 cells

The oleoresin myrrh has been used for centuries as an anti-inflammatory remedy for a variety of diseases and is said to have a protective effect on the intestinal epithelium. An intact epithelial barrier function is the prerequisite for a healthy gut. Inflammatory and infectious diseases of the intestine, in particular, lead to barrier impairment resulting in leak-flux diarrhea and mucosal immune responses. Therefore, the aim of the present study was to investigate the protective effect of myrrh in an experimental inflammatory situation, namely, under the influence of IL-13, one of the key cytokines in ulcerative colitis. We used human intestinal epithelial HT-29/B6 cell monolayers for functional and molecular assessment of the epithelial barrier under IL-13 and myrrh treatment. IL-13 induced a loss in barrier function that was fully restored with myrrh treatment, as shown by transepithelial electrical resistance measurements. The molecular correlate of the IL-13-mediated barrier dysfunction could be assigned to an upregulation of the channel-forming tight junction (TJ) protein claudin-2 and to a subcellular redistribution of the TJ protein tricellulin, loosening the sealing of tricellular TJs. Moreover, IL-13 exposure leads to an increase in the number of apoptotic cells, contributing to the leak pathway of barrier dysfunction. Myrrh protected against changes in TJ deregulation and decreased the elevated apoptotic ratio under IL-13. The protective effects are mediated through the inhibition of the STAT3 and STAT6 pathway. In conclusion, our results demonstrate that myrrh exhibits antagonizing effects against IL-13-induced barrier impairment in a human intestinal cell model. These data suggest the use of myrrh as a promising option in the treatment of inflammatory bowel disease.

Self-Double-Emulsifying Drug Delivery System Enteric-Coated Capsules: A Novel Approach to Improve Oral Bioavailability and Anti-inflammatory Activity of Panax notoginseng Saponins

In this work, self-double-emulsifying drug delivery system enteric-coated capsules (PNS-SDE-ECC) were used to enhance the oral bioavailability and anti-inflammatory effects of Panax notoginseng saponins (PNS), which are rapidly biodegradable, poorly membrane permeable, and highly water-soluble compounds. The PNS-SDEDDS formulated by a modified two-step method spontaneously emulsified to W/O/W double emulsions in the outer aqueous solution, which significantly promoted the absorption of PNS in the intestinal tract. The release study revealed that PNS-SDE-ECC exhibited sustained release of PNS within 24 h and the stability study indicated that PNS-SDE-ECC were stable at room temperature for up to 3 months. Furthermore, compared to PNS gastric capsules, the relative bioavailability of NGR1, GRg1, GRe, GRb1, and GRd in PNS-SDE-ECC was increased by 4.83, 10.78, 9.25, 3.58, and 4.63 times, respectively. More importantly, PNS-SDE-ECC significantly reduced OXZ-induced inflammatory damage in the colon by regulating the expression of TNF-α, IL-4, IL-13, and MPO cytokines. Overall, the prepared PNS-SDE-ECC may serve as a viable vehicle for increasing the oral bioavailability of PNS and its anti-inflammatory action on ulcerative colitis.

Alleviative mechanism and effect of Bifidobacterium animalisA6 on dextran sodium sulfate-induced ulcerative colitis in mice

Probiotics have been increasingly investigated for their role in alleviating symptoms of ulcerative colitis (UC), but the specific mechanism involved remains unclear. We investigated the alleviating effect of Bifidobacterium animalis A6 (BAA6) in UC through a mouse dextran sulfate sodium (DSS) model. When treated with a high dose of BAA6 (1 × 10¹⁰ cfu/ml), it was found that colitis symptoms were significantly alleviated, and mucosal damages experienced obvious relief. Moreover, a high dose of BAA6 effectively upregulated free fatty acid receptors 2 and 3 (FFAR2 and FFAR3) expression and butyric acid metabolism specifically. Furthermore, the supplement of BAA6 significantly suppressed pro-inflammatory cytokines levels (interleukin-13) and the expression of pore-forming protein claudin-2. The upstream regulatory genes of claudin-2, such as STAT6, GATA4, Cdx2, were also significantly inhibited by BAA6. Collectively, this study concludes that BAA6 attenuated DSS-induced colitis by increasing the levels of intestinal butyric acid, activating the butyric acid-FFAR pathway, suppressing excessive proinflammatory response, and protecting the function of the colon epithelial barrier.

Direct Action of Non-Digestible Oligosaccharides against a Leaky Gut

The epithelial monolayer is the primary determinant of mucosal barrier function, and tight junction (TJ) complexes seal the paracellular space between the adjacent epithelial cells and represent the main "gate-keepers" of the paracellular route. Impaired TJ functionality results in increased permeation of the "pro-inflammatory" luminal contents to the circulation that induces local and systemic inflammatory and immune responses, ultimately triggering and/or perpetuating (chronic) systemic inflammatory disorders. Increased gut leakiness is associated with intestinal and systemic disease states such as inflammatory bowel disease and neurodegenerative diseases such as Parkinson's disease. Modulation of TJ dynamics is an appealing strategy aiming at inflammatory conditions associated with compromised intestinal epithelial function. Recently there has been a growing interest in nutraceuticals, particularly in non-digestible oligosaccharides (NDOs). NDOs confer innumerable health benefits via microbiome-shaping and gut microbiota-related immune responses, including enhancement of epithelial barrier integrity. Emerging evidence supports that NDOs also exert health-beneficial effects on microbiota independently via direct interactions with intestinal epithelial and immune cells. Among these valuable features, NDOs promote barrier function by directly regulating TJs via AMPK-, PKC-, MAPK-, and TLR-associated pathways. This review provides a comprehensive overview of the epithelial barrier-protective effects of different NDOs with a special focus on their microbiota-independent modulation of TJs.

Proinflammatory role of basophils in oxazolone-induced chronic intestinal inflammation

BACKGROUND AND AIM

The functions of basophils have not been elucidated until recently because of their rarity. However, with recent developments in basophil-specific antibodies and basophil-deficient animals, the roles of basophils in various diseases related to chronic inflammation have been clarified. In this study, we aimed to investigate the roles of basophils in human ulcerative colitis (UC) and oxazolone (OXA) colitis using genetically engineered Mcpt8^DTR mice.

METHODS

Immunohistochemical staining of human colon specimens was performed to examine the involvement of basophils in the pathogenesis of UC. We examined the correlation between the number of infiltrating basophils and the UC endoscopic index of severity (UCEIS), Mayo score, and Matts score. We also examined the correlation between eosinophil count and basophil infiltration. In murine experiments, we examined whether basophil infiltration was involved in OXA-induced colitis and whether basophil depletion improved inflammation in Mcpt8^DTR mice.

RESULTS

Colonic basophil infiltration was significantly increased in patients with UC. There were significant correlations between UCEIS, Mayo score, Matts score, and the number of infiltrating basophils. In murine OXA-induced colitis, a significant increase in basophil infiltration was observed. When basophils were depleted by diphtheria toxin in Mcpt8^DTR mice, inflammation improved significantly and mRNA expression of some proinflammatory cytokines, including Tnf-α and Ifn-γ decreased significantly.

CONCLUSION

Basophil infiltration correlated with endoscopic, clinical, and pathological scores in human UC independently of eosinophil infiltration, and depletion of basophils ameliorated mucosal inflammation in murine OXA-induced colitis, collectively suggesting that basophils exert a proinflammatory role in chronic intestinal inflammation such as UC.

Serum IL-13 Predicts Response to Golimumab in Bio-Naïve Ulcerative Colitis

A certain number of patients with ulcerative colitis (UC) are refractory to anti-TNF-α antibodies; biomarkers are thus needed to predict treatment efficacy. This study aimed to evaluate whether serum biomarkers that were reported to be associated with UC or anti-TNF-α antibody could predict the response to golimumab, a human anti-TNF-α monoclonal antibody, in bio-naïve patients with UC. We prospectively enrolled 23 consecutive patients with UC who were treated with golimumab. Serum samples were collected before the first golimumab dose. Eleven molecules were measured by electrochemiluminescence (ECL) or enzyme-linked immunosorbent assay (ELISA) and their association with efficacy after 10 weeks of golimumab treatment. Among the serum biomarkers, IL-13 levels were significantly higher in the non-remission group than in the remission group (p = 0.014). IL-15 levels were significantly lower in the non-response group than in the response group (p = 0.04). For clinical remission at week 10, the IL-13 0.20 concentration of pg/mL was associated with a sensitivity and specificity of 82.4% and 83.3%, respectively. Serum IL-13 may be a biomarker to predict golimumab efficacy in biologic-naïve patients with UC, and thus may help to tailor personalized treatment strategies.

Glucocorticoid induced group 2 innate lymphoid cell overactivation exacerbates experimental colitis

Abnormal activation of the innate and adaptive immune systems has been observed in inflammatory bowel disease (IBD) patients. Anxiety and depression increase the risk of IBD by activating the adaptive immune system. However, whether anxiety affects innate immunity and its impact on IBD severity remains elusive. This study investigated the mechanism by which anxiety contributes to IBD development in a murine model of acute wrap restraint stress (WRS). Here, we found that anxiety-induced overactivation of group 2 innate lymphoid cells (ILC2) aggravated colonic inflammation. Overactivation of the hypothalamic–pituitary–adrenal (HPA) axis is a hallmark of the physiological change of anxiety. Corticosterone (CORT), a stress hormone, is a marker of HPA axis activation and is mainly secreted by HPA activation. We hypothesized that the overproduction of CORT stimulated by anxiety exacerbated colonic inflammation due to the abnormally elevated function of ILC2. The results showed that ILC2 secreted more IL-5 and IL-13 in the WRS mice than in the control mice. Meanwhile, WRS mice experienced more body weight loss, shorter colon length, higher concentrations of IL-6 and TNF-α, more severely impaired barrier function, and more severe inflammatory cell infiltration. As expected, the serum corticosterone levels were elevated after restraint stress. Dexamethasone (DEX) was then injected to mimic HPA axis activation induced CORT secretion. DEX injection can also stimulate ILC2 to secrete more type II cytokines and exacerbate oxazolone (OXA) induced colitis. Blocking the IL-13/STAT6 signaling pathway alleviated colitis in WRS and DEX-injected mice. In conclusion, the overactivation of ILC2 induced by CORT contributed to the development of OXA-induced colitis in mice.

The potential role of Bifidobacterium spp. as a preventive and therapeutic agent in controlling inflammation via affecting inflammatory signalling pathways

Inflammatory bowel disease (IBD) is a chronic inflammatory disease with relapses and periods of remission. Forasmuch as, dysregulation of the immune system is one of the triggers of IBD, taking probiotics as one of the immunomodulators in the gut, could help to control inflammation and IBD via influencing signalling pathways. Here, we aimed to investigate the efficacy of five selected Bifidobacterium strains in modulating JAK/STAT and NF-kB inflammatory signalling pathways via using the in vitro assay. A quantitative real-time polymerase chain reaction assay was used to analyse the expression of JAK/STAT and inflammatory genes followed by potential probiotic treatments before, after and simultaneously with the inflammation induction (sonicated pathogen). The production of IL-6 and IL-1β after probiotic treatment was evaluated. Probiotic treatment resulted in the downregulation of TIRAP, IRAK4, NEMO and RIP genes in the NF-kB pathway, as well as JAK genes compared to sonicate-treated cells. The expression of STAT genes was different after our selected Bifidobacterium strains treatment. The production of IL-6 and IL-1β decreased after probiotic treatment. These strains of Bifidobacterium spp. showed anti-inflammatory effects on HT-29 cells via modulation of JAK/STAT and NF-kB signalling pathways. The use of Bifidobacterium spp. could be considered as a suitable preventive and complementary treatment for patients with inflammatory bowel disease.

Anti‐inflammatory and immunomodulatory effects of Lactobacillus spp. as a preservative and therapeutic agent for IBD control

Background

Methods

Results

Conclusions

Keratin 1 maintains the intestinal barrier in ulcerative colitis

BACKGROUND

The intestinal mechanical barrier plays a key role in the pathogenesis of ulcerative colitis (UC). Our previous study showed keratin 1 (KRT1) was downregulated in UC, but the mechanism by which KRT1 affects the intestinal barrier remains unknown.

OBJECTIVES

To explore the mechanism of KRT1 in the intestinal barrier in UC.

METHODS

Colonic tissues were collected from 20 UC patients before and after mucosal healing (MH) and 15 healthy controls. The expression of KRT1 was measured by PCR, western blotting and immunohistochemistry (IHC). A dextran sulfate sodium (DSS)-induced colitis model was established in krt1 transgenic (TG) mice, and the mice were treated with methylprednisolone (MP) to explore the role of KRT1 in the intestinal barrier. Inflammation was evaluated through the DAI score, colon, spleen and H&E. The expression of KRT1 and tight junction (TJ) proteins in mouse was analysed by the same methods.

RESULTS

The transcription and expression of KRT1 in UC was decreased and recovered after MH but did not reach the level of the healthy controls. Similar to the clinical results, the expression of krt1 was decreased in DSS-induced colitis and upregulated after MP. Moreover, the krt1 TG group exhibited less inflammation than wild-type (WT) group. The expression of Occludin and ZO-1 decreased after DSS induction, the decreases in Occludin and ZO-1 in the krt1 TG group were lower than WT group, which was significantly increased after MP, while the expression of Claudin-2 exhibited the opposite effect.

CONCLUSIONS

Keratin 1 maintains the intestinal barrier by upregulating TJ proteins in UC.

Effects of cigarette smoke on the aggravation of ovalbumin-induced asthma and the expressions of TRPA1 and tight junctions in mice

The occurrence of asthma is closely related to environmental factors such as cigarette smoke (CS), one of the common risk factors. Environmental stimuli have the potential to activate transient receptor potential ankyrin 1 (TRPA1) and cause or aggravate asthma. The destruction of tight junctions (TJs) between airway epithelial cells by environmental stimuli in asthma has been researched. It is worth exploring whether CS can injury TJs and aggravate asthma by activating TRPA1. The objective of this study was to investigate the aggravation of CS on ovalbumin (OVA)-induced asthma related phenotypes and TJs expression in mice, and to explore the relationship between TRPA1 and the expression of TJs protein. Female wild type (WT) C57BL/6 mice, induced by OVA, CS and OVA plus CS (OVA + CS) respectively, were used to establish a 42-day asthma model, and mice with TRPA1 knockout (TRPA1-/-) were treated in the same way. This study detected the number of inflammatory cells in peripheral blood and bronchoalveolar lavage fluid (BALF), the levels of IL-4, IL-5, IL-13 in BALF, enhanced pause (Penh) of lung function, pathological changes and the gene and protein expressions of TRPA1 and TJs (including ZO-1, Occludin and Claudin-2) in lung tissues. Compared with normal saline (NS) group, WT mice in the OVA group and OVA + CS group were significantly higher in asthma related phenotypes. The WT-OVA + CS group also showed higher Penh value, levels of IL-5 and IL-13 in BALF and lung tissue injury scores when compared with the WT-OVA group and WT-CS group. However, WT-OVA + CS group mice had significantly larger number of neutrophils in BALF than the WT-OVA group, and had larger number of eosinophils in peripheral blood and higher levels of IL-4 in BALF than the WT-CS group. Meanwhile, compared with the WT-NS group, the expressions of TRPA1 and Claudin-2 in lung tissues increased in other three groups while their expressions of ZO-1 and Occludin decreased, among which, the WT-OVA + CS group showed more remarkable changes. Compared with the WT-OVA + CS group, mice in the TRPA1-/--OVA + CS showed a significant decrease in the number of inflammatory cells, levels of IL-4, IL-5 and IL-13 in BALF, Penh value and lung tissue injury score, and a downregulation of Claudin-2 expression while an upregulation of ZO-1 and Occludin expressions. In addition, the airway inflammation and injury, and the expressions of ZO-1, Occluding and Claudin-2 expressions were found with no statistic differences between TRPA1-/--OVA group and TRPA1-/--OVA + CS group. These results suggest that CS has aggravated the airway inflammation, pathological damage and destruction of TJs in airway epithelium of OVA-induced asthmatic mice, the processes of which are related to the increase of TRPA1 expression.

Phytochemicals Targeting JAK-STAT Pathways in Inflammatory Bowel Disease: Insights from Animal Models

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract that consists of Crohn’s disease (CD) and ulcerative colitis (UC). Cytokines are thought to be key mediators of inflammation-mediated pathological processes of IBD. These cytokines play a crucial role through the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) signaling pathways. Several small molecules inhibiting JAK have been used in clinical trials, and one of them has been approved for IBD treatment. Many anti-inflammatory phytochemicals have been shown to have potential as new drugs for IBD treatment. This review describes the significance of the JAK–STAT pathway as a current therapeutic target for IBD and discusses the recent findings that phytochemicals can ameliorate disease symptoms by affecting the JAK–STAT pathway in vivo in IBD disease models. Thus, we suggest that phytochemicals modulating JAK–STAT pathways are potential candidates for developing new therapeutic drugs, alternative medicines, and nutraceutical agents for the treatment of IBD.

STAT6 Is Critical for the Induction of Regulatory T Cells In Vivo Controlling the Initial Steps of Colitis-Associated Cancer

Inflammation is the main driver of the tumor initiation and progression in colitis-associated colorectal cancer (CAC). Recent findings have indicated that the signal transducer and activator of transcription 6 (STAT6) plays a fundamental role in the early stages of CAC, and STAT6 knockout (STAT6^−/−) mice are highly resistant to CAC development. Regulatory T (Treg) cells play a major role in coordinating immunomodulation in cancer; however, the role of STAT6 in the induction and function of Treg cells is poorly understood. To clarify the contribution of STAT6 to CAC, STAT6^−/− and wild type (WT) mice were subjected to an AOM/DSS regimen, and the frequency of peripheral and local Treg cells was determined during the progression of CAC. When STAT6 was lacking, a remarkable reduction in tumor growth was observed, which was associated with decreased inflammation and an increased number of CD4+CD25+Foxp3+ cells in the colon, circulation, and spleen, including an over-expression of TGF-beta, IL-10, and Foxp3, compared to WT mice, during the early stages of CAC development. Conversely, WT mice showed an inverse frequency of Treg cells compared with STAT6^−/− mice, which was followed by intestinal tumor formation. Increased mucosal inflammation, histological damage, and tumorigenesis were restored to levels observed in WT mice when an early inhibition/depletion of Treg cells was performed in STAT6^−/− mice. Thus, with STAT6 deficiency, an increased number of Treg cells induce resistance against tumorigenesis, arresting tumor-promoting inflammation. We reported a direct role of STAT6 in the induction and function of Treg cells during CAC development and suggest that STAT6 is a potential target for the modulation of immune response in colitis and CAC.

STAT6 rs324015 Gene Polymorphism Increases Ulcerative Colitis Risk: A Case-Control Study

Introduction

Phosphorylation of signal transducer and activator of transcription 6 (STAT6) in the colonic epithelium is elevated in ulcerative colitis (UC) patients, and its inhibition prevents IL-13-associated apoptosis and barrier disruption. Recently, the STAT6 rs324015 polymorphism was reported to be related to genetic susceptibility to UC.

Methods

We examined STAT6 rs324015 using the PCR–RFLP method in 268 UC cases and 357 controls. STAT6 expression was determined by quantitative reverse-transcription PCR. The gene–environment interactions were addressed by cross-over analysis.

Results

We found that the STAT6 rs324015 polymorphism enhanced the risk of UC under the homozygous, dominant, and allelic models. Further subgroup analyses indicated that this relationship was more evident in alcohol users, smokers, and those younger than 40 years. Cross-over analysis showed strong interactions of STAT6 rs324015 with smoking/alcohol use. In addition, this polymorphism was associated with the severity, and location of UC. The GG genotype was significantly associated with increased STAT6 gene levels.

Conclusion

In summary, the STAT6 rs324015 polymorphism is related with predisposition to UC in a Chinese Han population.

Differential regulation of JAK/STAT-signaling in patients with ulcerative colitis and Crohn’s disease

In 2018, the pan-Janus kinase (JAK) inhibitor tofacitinib was launched for the treatment of ulcerative colitis (UC). Although tofacitinib has proven efficacious in patients with active UC, it failed in patients with Crohn’s disease (CD). This finding strongly hints at a different contribution of JAK signaling in both entities. Here, we review the current knowledge on the interplay between the JAK/signal transducer and activator of transcription (STAT) pathway and inflammatory bowel diseases (IBD). In particular, we provide a detailed overview of the differences and similarities of JAK/STAT-signaling in UC and CD, highlight the impact of the JAK/STAT pathway in experimental colitis models and summarize the published evidence on JAK/STAT-signaling in immune cells of IBD as well as the genetic association between the JAK/STAT pathway and IBD. Finally, we describe novel treatment strategies targeting JAK/STAT inhibition in UC and CD and comment on the limitations and challenges of the new drug class.

Vitamin D regulates claudin-2 and claudin-4 expression in active ulcerative colitis by p-Stat-6 and Smad-7 signaling

PURPOSE

The tight junctions (TJ) responsible for the integrity of the intestinal barrier are altered in patients with inflammatory bowel disease (IBD), but the physiopathological mechanisms that lead to this alteration are not yet clear. The aim of this study was to determine whether vitamin D, which regulates the integrity of the epithelial barrier by expressing TJ proteins, reduces claudin-2 (Cl-2) levels by inhibiting Stat-6 phosphorylation and whether it increases claudin-4 (Cl-4) levels by blocking Smad-7 activity.

METHODS

Biopsies were obtained from inflamed and non-inflamed tracts of the right side colon (caecum or ascending colon) from the same patient with active UC. All the patients were affected by a recent flare-up of ulcerative rectocolitis (RCU), with no previous biologic or immunosuppressive therapy, and all the biopsies were obtained before any treatments. The biopsies were cultured in the presence or not of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃). We also used T84 cells as an in vitro model to perform transfection experiments with Stat-6 and Smad-7.

RESULTS

Our results indicate that 1,25(OH)₂D₃ is able to regulate CL-2 and CL-4 protein levels, which are increased and reduced in the intestinal mucosa of UC patients, respectively. In the biopsies obtained from UC patients 1,25(OH)₂D₃ reduces Cl-2 levels by blocking Stat-6 phosphorylation and increases Cl-4 levels by blocking Smad-7 activity. T84 cells, transfected with siRNA of Stat-6 and Smad-7, showed reduced Cl-2 levels and increased Cl-4 levels, confirming that 1,25(OH)₂D₃ regulates Cl-2 and Cl-4 by decreasing p-Stat-6 and Smad-7 levels.

CONCLUSIONS

Our results indicate that the effects of vitamin D on Cl-2 and Cl-4 are mediated by p-Stat-6 and Smad-7 signal, respectively. The study suggests that vitamin D administration to UC patients could be a useful therapeutic intervention, given that vitamin D deficiency is found in these patients.

Intestinal vitamin D receptor knockout protects from oxazolone-induced colitis

Crohn’s disease (CD) and ulcerative colitis (UC) actually had different pathological mechanisms, as the former was mainly induced by Th1 and Th17 response and the latter by Th2 response. Our previous study found that oxazolone-induced Th2-mediated colitis could not be attenuated by vitamin D supplementation. This study investigated the influence of intestinal vitamin D receptor (VDR) knockout on oxazolone-induced colitis and explored the possible immunological mechanism. Intestinal VDR knockout mice had milder oxazolone-induced colitis than wildtype controls, as demonstrated by less body weight decrease and faster recovery, more intact local structure, reduced cell apoptosis, and better preserved barrier function. Th2-mediated inflammation was significantly inhibited by VDR deficiency. Meanwhile, the percentage of invariant natural killer T (iNKT) cells did not increase as much in intestinal VDR knockout mice as in wild-type controls, nor did the iNKT cells develop normally as in the controls. Intestinal VDR knockout protected against oxazolone-induced colitis in mice by blocking Th2 cell response and reducing the function of intestinal iNKT cells. Vitamin D status had no influence on the severity of colitis. This study may explain the diverse outcomes after vitamin D supplementation in literature and add some clue to the targeted therapy of IBD.

JAK-STAT pathway targeting for the treatment of inflammatory bowel disease

Cytokines are involved in intestinal homeostasis and pathological processes associated with inflammatory bowel disease (IBD). The biological effects of cytokines, including several involved in the pathology of Crohn's disease and ulcerative colitis, occur as a result of receptor-mediated signalling through the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) DNA-binding families of proteins. Although therapies targeting cytokines have revolutionized IBD therapy, they have historically targeted individual cytokines, and an unmet medical need exists for patients who do not respond to or lose response to these treatments. Several small-molecule inhibitors of JAKs that have the potential to affect multiple pro-inflammatory cytokine-dependent pathways are in clinical development for the treatment of IBD, with one agent, tofacitinib, already approved for ulcerative colitis and several other agents with demonstrated efficacy in early phase trials. This Review describes the current understanding of JAK-STAT signalling in intestinal homeostasis and disease and the rationale for targeting this pathway as a treatment for IBD. The available evidence for the efficacy, safety and pharmacokinetics of JAK inhibitors in IBD as well as the potential approaches to optimize treatment with these agents, such as localized delivery or combination therapy, are also discussed.

Signal transducer and activator of transcription 6 as a target in colon cancer therapy

Signal transducer and activator of transcription 6 (STAT6) is a member of the STAT family of proteins that serve key roles in the initiation of tumorigenesis and malignant transformation. STAT6 is highly expressed in several types of cancer, including breast, pancreatic, prostate and colorectal cancer. STAT6 transduces signals in response to the binding of interleukin (IL)-4 and IL-13 to their receptors and regulates the expression of genes involved in the immune response, cell survival, tumor proliferation and metastasis. Patients with colorectal cancer exhibit high STAT6 activity in the colonic epithelium, and STAT6 expression is associated with lower survival rates, lymph node metastasis, changes in the epithelial barrier function and alterations in the inflammatory response. A number of studies investigating experimental models and cancer cell lines have revealed that STAT6 is associated with tumor growth and development, as well as with increased invasion and metastasis, suggesting that STAT6 inhibition may serve as a novel therapeutic strategy in colon cancer. The present review summarizes the evidence with regard to the implications of STAT6 in cancer biology and the direct and indirect effects on colon tumor transformation. Furthermore, the current treatment strategies targeting the IL-4/IL-13/STAT6 axis in colon cancer are discussed.

The JAK-Inhibitor Tofacitinib Rescues Human Intestinal Epithelial Cells and Colonoids from Cytokine-Induced Barrier Dysfunction

BACKGROUND

Alterations to epithelial tight junctions can compromise the ability of the epithelium to act as a barrier between luminal contents and the underlying tissues, thereby increasing intestinal permeability, an early critical event in inflammatory bowel disease (IBD). Tofacitinib (Xeljanz), an orally administered pan-Janus kinase (JAK) inhibitor, was recently approved for the treatment of moderate to severe ulcerative colitis. Nevertheless, the effects of tofacitinib on intestinal epithelial cell functions are largely unknown. The aim of this study was to determine if JAK inhibition by tofacitinib can rescue cytokine-induced barrier dysfunction in intestinal epithelial cells (IECs).

METHODS

T84 IECs were used to evaluate the effects of tofacitinib on JAK-signal transducer and activator of transcription (STAT) activation, barrier permeability, and expression and localization of tight junction proteins. The impact of tofacitinib on claudin-2 promoter activity was assessed in HT-29 IECs. Tofacitinib rescue of barrier function was also tested in human colonic stem cell-derived organoids.

RESULTS

Pretreatment with tofacitinib prevented IFN-γ-induced decreases in transepithelial electrical resistance (TER) and increases in 4 kDa FITC-dextran permeability (FD4), partly due to claudin-2 transcriptional regulation and restriction of ZO-1 rearrangement at tight junctions. Although tofacitinib administered after IFN-γ challenge only partially normalized TER and claudin-2 levels, FD4 permeability and ZO-1 localization were fully recovered. The IFN-γ-induced FD4 permeability in primary human colonoids was fully rescued by tofacitinib.

CONCLUSIONS

These data suggest differential therapeutic efficacy of tofacitinib in the rescue of pore vs leak-tight junction barrier defects and indicate a potential contribution of improved epithelial barrier function to the beneficial effects of tofacitinib in IBD patients.

Tight junctions in the development of asthma, chronic rhinosinusitis, atopic dermatitis, eosinophilic esophagitis, and inflammatory bowel diseases

This review focuses on recent developments related to asthma, chronic rhinosinusitis, atopic dermatitis (AD), eosinophilic esophagitis, and inflammatory bowel diseases (IBD), with a particular focus on tight junctions (TJs) and their role in the pathogenetic mechanisms of these diseases. Lung, skin, and intestinal surfaces are lined by epithelial cells that interact with environmental factors and immune cells. Therefore, together with the cellular immune system, the epithelium performs a pivotal role as the first line physical barrier against external antigens. Paracellular space is almost exclusively sealed by TJs and is maintained by complex protein-protein interactions. Thus, TJ dysfunction increases paracellular permeability, resulting in enhanced flux across TJs. Epithelial TJ dysfunction also causes immune cell activation and contributes to the pathogenesis of chronic lung, skin, and intestinal inflammation. Characterization of TJ protein alteration is one of the key factors for enhancing our understanding of allergic diseases as well as IBDs. Furthermore, TJ-based epithelial disturbance can promote immune cell behaviors, such as those in dendritic cells, Th2 cells, Th17 cells, and innate lymphoid cells (ILCs), thereby offering new insights into TJ-based targets. The purpose of this review is to illustrate how TJ dysfunction can lead to the disruption of the immune homeostasis in barrier tissues and subsequent inflammation. This review also highlights the various TJ barrier dysfunctions across different organ sites, which would help to develop future drugs to target allergic diseases and IBD.

IL-4 Receptor-Alpha Signalling of Intestinal Epithelial Cells, Smooth Muscle Cells, and Macrophages Plays a Redundant Role in Oxazolone Colitis

A hallmark of ulcerative colitis is the chronic colonic inflammation, which is the result of a dysregulated intestinal mucosal immune response. Epithelial barrier disruption which allows the entry of microorganisms eventually leads to more aggressive inflammation and potentially the removal of the colon. We have previously shown that the T helper- (Th-) type 2 cytokines, Interleukin- (IL-) 4 and IL-13, mediate CD4+ T cell- or B cell-driven inflammation in the oxazolone-induced mouse model of ulcerative colitis. In contrast, mice deficient in the shared receptor of IL-4 and IL-13, IL-4 receptor-alpha (IL-4Rα), on all cells develop an exacerbated disease phenotype. This suggests that a regulatory role of IL-4Rα is required to protect against severe colitis. However, the cell populations responsible for regulating the severity of disease onset through IL-4Rα in colitis are yet to be identified. By deleting IL-4Rα on specific cell subsets shown to play a role in mediating colitis, we determined their role in a loss of function approach. Our data demonstrated that the loss of IL-4Rα signalling on intestinal epithelial cells, smooth muscle cells, and macrophages/neutrophils had no effect on alleviating the pathology associated with colitis. These results suggest that IL-4/IL-13 signalling through IL-4Rα on nonhematopoietic intestinal epithelial or smooth muscle cells and hematopoietic macrophage/neutrophils has a redundant role in driving acute oxazolone colitis.

Improvement of Oxazolone-Induced Ulcerative Colitis in Rats Using Andrographolide

Ulcerative colitis (UC) is usually accompanied with symptoms of abdominal pain, diarrhea, and bloody stool, which impair the quality of life of patients. Previous studies have shown that Andrographis paniculata extracts, which have andrographolide (AND) as their main compound, can relieve UC symptoms in patients. The aim of the study was to investigate the alleviating effect of AND on UC using the oxazolone (OXZ)-induced UC rat model. A total of 66 healthy male Sprague Dawley rats were used to evaluate the efficacy and mechanism of AND on UC (n = 11 per group) and grouped into control, model, SASP (sulfasalazine, positive control group, 500 mg/kg), AND-L (40 mg/kg), AND-M (80 mg/kg), and AND-H (120 mg/kg). The colonic disease activity index (DAI), colon length, spleen coefficient, pathological damage, and inflammation-related cytokine and protein expression levels were used as indices for evaluation. Results showed that the AND groups had reduced DAI and mortality, and significantly improved colon length and spleen coefficient compared with the model group. Furthermore, OXZ-induced histological injury was relieved significantly after AND treatment due to an improved crypt structure and reduced infiltration of inflammatory cells. Moreover, AND inhibited myeloperoxidase (MPO) activity and the secretion of interleukin-4 (IL-4), IL-13, and tumor necrosis factor α (TNF-α). The results of the anti-inflammatory mechanism revealed that AND blocked the signal transduction by reducing IL-4/IL-13 specific binding to IL-4 receptor (IL-4R) and inhibiting the phosphorylation of the signal transducer and activator of transcription 6 (p-STAT6). In conclusion, aside from natural plants, AND may be a candidate ingredient for UC therapy.

NEAT1 regulates Th2 cell development by targeting STAT6 for degradation

The aim of this study was to investigate the role of lncRNA NEAT1 (nuclear enriched abundant transcript 1) in regulating Th2 cell differentiation. The overexpression vectors of NEAT1 and ITCH, and siRNA targeting NEAT1, EZH2 (enhancer of zeste homolog 2) and STAT6 (signal transducer and activator of transcription 6) were transfected into CD4+T cells. The mRNA expressions of ITCH and STAT6 were analyzed by qRT-PCR and western blotting. The levels of Th2 cytokines were detected by ELISA assay. RIP and ChIP assays were performed to analyze the association between NEAT1 and EZH2 as well as EZH2 and STAT6, respectively. Results showed that NEAT1 significantly repressed ITCH expression and increased STAT6 expression as well as the levels of IL-4, IL-5 and IL-13 in CD4+T cells. RIP and ChIP assays revealed that NEAT1 bound to EZH2 and EZH2 was recruited to the promoter region of ITCH in CD4+T cells. Silencing EZH2 significantly promoted STAT6 for ubiquitination. Furthermore, NEAT targeted STAT6 for ubiquitination and elevated levels of Th2 cytokines by regulating EZH2/ITCH axis. In conclusion, our data indicated that NEAT1 promotes Th2 cell differentiation through the EZH2/ITCH/STAT6 axis.

Targeting IL-13 as a Host-Directed Therapy Against Ulcerative Colitis

The role of interleukin-13 in mediating ulcerative colitis remains under scrutiny. Compelling evidence from both man and mouse suggests that IL-13 not only contributes to the pathology associated with disease but is also involved in mediating the inflammatory response. These studies have led to the approach of targeting IL-13 as a promising treatment strategy in alleviating ulcerative colitis disease. Despite this evidence, recent clinical trial data suggests that specifically blocking the receptor through which IL-13 signals, IL-4 receptor-alpha (IL-4Rα) in ulcerative colitis patients, is insufficient in protecting them from disease outcome. This challenges the importance of IL-13 as a therapeutic target. This review describes the role of IL-13 in ulcerative colitis and current treatment strategies that target IL-13. The potential role of IL-13 signaling independently of IL-4Rα in mediating ulcerative colitis is highlighted as an important consideration when targeting the signaling mechanisms of IL-13 for therapeutic approaches.

Natural killer T cells and ulcerative colitis

Ulcerative colitis (UC) is one of the two major forms of inflammatory bowel disease (IBD). Both innate immunity and adaptive immunity are aberrant in IBD. The pathogenesis of UC includes abnormal inflammation and immune responses of the digestive tract. Natural killer T (NKT) cells participate in the innate and adaptive immune responses, together with a vast array of cytokines. Recent studies suggested that IL-13, IL5 and IL-4 are involved in the occurrence and the development of UC. Manipulating NKT cells may be a potential strategy to reconstruct the abnormal immune responses in UC. In this review, we explore the roles of NKT cells and cytokines in UC. Additionally, neutralizing antibodies and inhibitors of cytokines produced by NKT cells or their receptors are also discussed as novel therapeutic choices for UC.

Effector T Helper Cell Subsets in Inflammatory Bowel Diseases

The gastrointestinal tract is a site of high immune challenge, as it must maintain a delicate balance between tolerating luminal contents and generating an immune response toward pathogens. CD4⁺ T cells are key in mediating the host protective and homeostatic responses. Yet, CD4⁺ T cells are also known to be the main drivers of inflammatory bowel disease (IBD) when this balance is perturbed. Many subsets of CD4⁺ T cells have been identified as players in perpetuating chronic intestinal inflammation. Over the last few decades, understanding of how each subset of Th cells plays a role has dramatically increased. Simultaneously, this has allowed development of therapeutic innovation targeting specific molecules rather than broad immunosuppressive agents. Here, we review the emerging evidence of how each subset functions in promoting and sustaining the chronic inflammation that characterizes IBD.

CD96 expression determines the inflammatory potential of IL-9-producing Th9 cells

T helper type (Th) 9 cells demonstrate both pro- and antiinflammatory properties, pointing to a functional heterogeneity not examined so far. Applying single cell gene expression analysis of alloreactive Th9 cells, we revealed the existence of two major subsets, CD96^high and CD96^low Th9 cells, with strongly opposing inflammatory and, especially, colitis-inducing potential. Mechanistically, we found that CD96 controls cytokine and colitis-inducing potential of Th9 cells, providing strong evidence for an inhibitory role of CD96 in controlling CD4⁺ T-cell effector functions. Thus, interfering with CD96-mediated immune inhibition would be a promising approach in preventing Th9-mediated diseases, such as ulcerative colitis, or reinforcement of Th9-mediated immune control of tumors and infections.

Recent findings demonstrated proinflammatory functions of interleukin (IL)-9–producing T helper type (Th) 9 cells in the pathogenesis of intestinal bowel diseases (IBDs). However, also antiinflammatory properties have been ascribed to Th9 cells, pointing to a functional heterogeneity. To dissect the specific expression pattern and, especially, diversity of murine antigen-specific Th9 cells, we applied single cell transcription profiling. Th9 cells displayed reduced expression of typical activation markers, such as Cd40 ligand and Cd96, whereas expression of Cd25 and Cd83 was increased compared with other Th subsets. Importantly, we identified two subsets of Th9 cells differing above all in their CD96 expression. The heterogeneous CD96 expression was specific for Th9 cells and not observed for other Th subtypes, such as Th1 cells. Lower CD96 expression was also observed in human IL-9⁺ compared with IFN-γ⁺ T cells. Although Il9 was highly transcribed by all Th9 cells, IL-9 mRNA and protein expression was increased in CD96^low cells. Transfer of CD96^low Th9 cells into recombination activating gene 1-deficient (Rag1^−/−) mice caused severe weight loss, intestinal and colonic inflammation, and destruction of allogeneic skin grafts and thus showed high inflammatory potential. This was associated with their expansion and tissue accumulation. Contrastingly, CD96^high Th9 cells did not cause colitis and showed reduced expansion and migratory potential. Blockade of CD96 completely restored the expansion and inflammatory properties of CD96^high Th9 cells. Collectively, our data suggest an inhibitory role for the cosignaling receptor CD96 in Th9 cells, raising new opportunities in the treatment of IL-9–associated inflammations such as IBD.

Substance-P Ameliorates Dextran Sodium Sulfate-Induced Intestinal Damage by Preserving Tissue Barrier Function

Intestinal inflammation alters immune responses in the mucosa and destroys colon architecture, leading to serious diseases such as inflammatory bowel disease. Thus, the modulation of intestinal integrity and immune responses in IBD can be the critical factor to be considered to reduce the severity of damages. Substance-P (SP), endogenous peptide to be involved in cell proliferation, migration and immune modulation, can exert the therapeutic effect on diverse diseases including cornea damage, rheumatoid arthritis and diabetic complications. SP was found to elevate expression of junctional molecule. Considering the function of SP reported previously, it was inferred that SP is capable of exert the beneficial effect of SP on intestinal diseases by controlling intestinal structure as well as immune responses. In this study, we explored the therapeutic effect of SP on dextran sodium sulfate-induced intestine damage by injecting SP. The effects of SP were evaluated by analyzing crypt structures, proliferating cell pool and infiltration of immune cells. DSS treatment provoked abnormal immune response and disruption of intestine epithelial barrier. However, co-treatment of SP obviously blocked the development of intestinal damages by declining inflammatory responses and sustaining intestinal structure more intact. The treatment of SP to chronic damages also promoted intestinal regeneration by preserving the integrity of colon tissue. Moreover, DSS-induced reduction of epithelial junctional molecule was obviously inhibited by SP treatment in vitro. Taken together, our data indicate that SP can reduce intestinal damages, possibly by modulating barrier structure and immune response. Our results propose SP as candidate therapeutics in intestinal damages.

T cell protein tyrosine phosphatase prevents STAT1 induction of claudin-2 expression in intestinal epithelial cells

T cell protein tyrosine phosphatase (TCPTP) dephosphorylates a number of substrates, including JAK-STAT (signal transducer and activator of transcription) signaling proteins, which are activated by interferon (IFN)-γ, a major proinflammatory cytokine involved in conditions such as inflammatory bowel disease. A critical function of the intestinal epithelium is formation of a selective barrier to luminal contents. The structural units of the epithelium that regulate barrier function are the tight junctions (TJs), and the protein composition of the TJ determines the tightness of the barrier. Claudin-2 is a TJ protein that increases permeability to cations and reduces transepithelial electrical resistance (TER). We previously showed that transient knockdown (KD) of TCPTP permits increased expression of claudin-2 by IFN-γ. Here, we demonstrate that the decreased TER in TCPTP-deficient epithelial cells is alleviated by STAT1 KD. Moreover, increased claudin-2 in TCPTP-deficient cells requires enhanced STAT1 activation and STAT1 binding to the CLDN2 promoter. We also show that mutation of this STAT-binding site prevents elevated CLDN2 promoter activity in TCPTP-deficient epithelial cells. In summary, we demonstrate that TCPTP protects the intestinal epithelial barrier by restricting STAT-induced claudin-2 expression. This is a potential mechanism by which loss-of-function mutations in the gene encoding TCPTP may contribute to barrier defects in chronic intestinal inflammatory disease.

Downregulation of miR-214-3p May Contribute to Pathogenesis of Ulcerative Colitis via Targeting STAT6

MicroRNAs (miRs) are small noncoding RNA molecules and recently have demonstrated that altered expression and functions are their tight association with ulcerative colitis (UC). Previous microarray study reported that miR-214 was downregulated in the sigmoid colon of patients with active UC, but the roles of miR-214 in the pathogenesis of UC remain to be elucidated. In this study, significant lower level of miR-214-3p and higher level of STAT6 in the intestinal mucosa of active UC patients compared with the health controls were confirmed by quantitative real-time PCR. Results of luciferase reporter assays and western blot demonstrated that miR-214-3p directly targets STAT6 and negatively regulates the expression of STAT6 at the posttranscriptional level. Furthermore, the expression of miR-214-3p was decreased in TNF-α treated HT29 cells and STAT6 protein level was increased in a time-dependent manner. Silenced STAT6 and upregulation of miR-214-3p could decrease the level of INF-γ in TNF-α treated HT29 cells. Additionally, the results of the present study indicate that miR-214-3p and STAT6 axis may be a novel therapeutic target for intestinal inflammation of patients with active UC.

IL-22 Upregulates Epithelial Claudin-2 to Drive Diarrhea and Enteric Pathogen Clearance

Diarrhea is a host response to enteric pathogens, but its impact on pathogenesis remains poorly defined. By infecting mice with the attaching and effacing bacteria Citrobacter rodentium, we defined the mechanisms and contributions of diarrhea and intestinal barrier loss to host defense. Increased permeability occurred within 2 days of infection and coincided with IL-22-dependent upregulation of the epithelial tight junction protein claudin-2. Permeability increases were limited to small molecules, as expected for the paracellular water and Na+ channel formed by claudin-2. Relative to wild-type, claudin-2-deficient mice experienced severe disease, including increased mucosal colonization by C. rodentium, prolonged pathogen shedding, exaggerated cytokine responses, and greater tissue injury. Conversely, transgenic claudin-2 overexpression reduced disease severity. Chemically induced osmotic diarrhea reduced colitis severity and C. rodentium burden in claudin-2-deficient, but not transgenic, mice, demonstrating that claudin-2-mediated protection is the result of enhanced water efflux. Thus, IL-22-induced claudin-2 upregulation drives diarrhea and pathogen clearance.

Inflammatory cytokines down-regulate the barrier-protective prostasin-matriptase proteolytic cascade early in experimental colitis

Compromised gastrointestinal barrier function is strongly associated with the progressive and destructive pathologies of the two main forms of irritable bowel disease (IBD), ulcerative colitis (UC), and Crohn's disease (CD). Matriptase is a membrane-anchored serine protease encoded by suppression of tumorigenicity-14 (ST14) gene, which is critical for epithelial barrier development and homeostasis. Matriptase barrier-protective activity is linked with the glycosylphosphatidylinositol (GPI)-anchored serine protease prostasin, which is a co-factor for matriptase zymogen activation. Here we show that mRNA and protein expression of both matriptase and prostasin are rapidly down-regulated in the initiating inflammatory phases of dextran sulfate sodium (DSS)-induced experimental colitis in mice, and, significantly, the loss of these proteases precedes the appearance of clinical symptoms, suggesting their loss may contribute to disease susceptibility. We used heterozygous St14 hypomorphic mice expressing a promoter-linked β-gal reporter to show that inflammatory colitis suppresses the activity of the St14 gene promoter. Studies in colonic T84 cell monolayers revealed that barrier disruption by the colitis-associated Th2-type cytokines, IL-4 and IL-13, down-regulates matriptase as well as prostasin through phosphorylation of the transcriptional regulator STAT6 and that inhibition of STAT6 with suberoylanilide hydroxamic acid (SAHA) restores protease expression and reverses cytokine-induced barrier dysfunction. Both matriptase and prostasin are significantly down-regulated in colonic tissues from human subjects with active ulcerative colitis or Crohn's disease, implicating the loss of this barrier-protective protease pathway in the pathogenesis of irritable bowel disease.

Intestinal epithelial claudins: expression and regulation in homeostasis and inflammation

The intestinal epithelium forms a highly dynamic and selective barrier that controls absorption of fluid and solutes while restricting pathogen access to underlying tissues. Barrier properties are achieved by intercellular junctions that include an apical tight junction (TJ) and subjacent adherens junctions and desmosomes. The TJ tetraspan claudin proteins form pores between epithelial cells to control paracellular fluid and ion movement. In addition to regulation of barrier function, claudin family members control epithelial homeostasis and are expressed in a spatiotemporal manner in the intestinal crypt-luminal axis. This delicate balance of physiologic differential claudin protein expression is altered during mucosal inflammation. Inflammatory mediators influence transcriptional regulation, as well as endocytic trafficking, targeting, and retention of claudins in the TJ. Increased expression of intestinal epithelial claudin-1, -2, and -18 with downregulation of claudin-3, -4, -5, -7, -8, and -12 has been observed in intestinal inflammatory disorders. Such changes in claudin proteins modify the epithelial barrier function in addition to influencing epithelial and mucosal homeostasis. An improved understanding of the regulatory mechanisms that control epithelial claudin proteins will provide strategies to strengthen the epithelial barrier function and restore mucosal homeostasis in inflammatory disorders.

Mucosal Expression of Type 2 and Type 17 Immune Response Genes Distinguishes Ulcerative Colitis From Colon-Only Crohn's Disease in Treatment-Naive Pediatric Patients

BACKGROUND & AIMS

There is controversy regarding the role of the type 2 immune response in the pathogenesis of ulcerative colitis (UC)-few data are available from treatment-naive patients. We investigated whether genes associated with a type 2 immune response in the intestinal mucosa are up-regulated in treatment-naive pediatric patients with UC compared with patients with Crohn's disease (CD)-associated colitis or without inflammatory bowel disease (IBD), and whether expression levels are associated with clinical outcomes.

METHODS

We used a real-time reverse-transcription quantitative polymerase chain reaction array to analyze messenger RNA (mRNA) expression patterns in rectal mucosal samples from 138 treatment-naive pediatric patients with IBD and macroscopic rectal disease, as well as those from 49 children without IBD (controls), enrolled in a multicenter prospective observational study from 2008 to 2012. Results were validated in real-time reverse-transcription quantitative polymerase chain reaction analyses of rectal RNA from an independent cohort of 34 pediatric patients with IBD and macroscopic rectal disease and 17 controls from Cincinnati Children's Hospital Medical Center.

RESULTS

We measured significant increases in mRNAs associated with a type 2 immune response (interleukin [IL]5 gene, IL13, and IL13RA2) and a type 17 immune response (IL17A and IL23) in mucosal samples from patients with UC compared with patients with colon-only CD. In a regression model, increased expression of IL5 and IL17A mRNAs distinguished patients with UC from patients with colon-only CD (P = .001; area under the receiver operating characteristic curve, 0.72). We identified a gene expression pattern in rectal tissues of patients with UC, characterized by detection of IL13 mRNA, that predicted clinical response to therapy after 6 months (odds ratio [OR], 6.469; 95% confidence interval [CI], 1.553-26.94), clinical response after 12 months (OR, 6.125; 95% CI, 1.330-28.22), and remission after 12 months (OR, 5.333; 95% CI, 1.132-25.12).

CONCLUSIONS

In an analysis of rectal tissues from treatment-naive pediatric patients with IBD, we observed activation of a type 2 immune response during the early course of UC. We were able to distinguish patients with UC from those with colon-only CD based on increased mucosal expression of genes that mediate type 2 and type 17 immune responses. Increased expression at diagnosis of genes that mediate a type 2 immune response is associated with response to therapy and remission in pediatric patients with UC.

Myrrh exerts barrier-stabilising and -protective effects in HT-29/B6 and Caco-2 intestinal epithelial cells

PURPOSE

Myrrh, the oleo-gum resin of Commiphora molmol, is well known for its anti-inflammatory properties. In different animal models, it protected against DSS-, TNBS- and oxazolone-induced colitis. To date, no information concerning the effect of myrrh on barrier properties are available. Thus, this study investigates the effect of myrrh on paracellular barrier function in the absence or presence of the pro-inflammatory cytokine TNFα.

METHODS

Monolayers of human colon cell lines HT-29/B6 and Caco-2 were incubated with myrrh under control conditions or after challenge with the pro-inflammatory cytokine TNFα. Barrier function was analysed by electrophysiological and permeability measurements, Western blotting, immunostaining in combination with confocal microscopy, and freeze-fracture electron microscopy.

RESULTS

In Caco-2 cells, myrrh induced an increase in transepithelial resistance (TER) which was associated with downregulation of the channel-forming tight junction (TJ) protein claudin-2 via inhibition of the PI3 kinase signalling pathway. In HT-29/B6 cells, myrrh had no effect on barrier properties under basic conditions, but protected against barrier damage induced by TNFα, as indicated by a decrease in TER and an increase in fluorescein permeability. The TNFα effect was associated with a redistribution of the sealing TJ protein claudin-1, an increase in the expression of claudin-2 and a change in TJ ultrastructure. Most importantly, all TNFα effects were inhibited by myrrh. The effect of myrrh on claudin-2 expression in this cell line was mediated via inhibition of the STAT6 pathway.

CONCLUSIONS

This study shows for the first time that myrrh exerts barrier-stabilising and TNFα-antagonising effects in human intestinal epithelial cell models via inhibition of PI3K and STAT6 signalling. This suggests therapeutic application of myrrh in intestinal diseases associated with barrier defects and inflammation.

Lack of STAT6 Attenuates Inflammation and Drives Protection against Early Steps of Colitis-Associated Colon Cancer

Colitis-associated colon cancer (CAC) is one of the most common malignant neoplasms and a leading cause of death. The immunologic factors associated with CAC development are not completely understood. Signal transducer and activator of transcription 6 (STAT6) is part of an important signaling pathway for modulating intestinal immune function and homeostasis. However, the role of STAT6 in colon cancer progression is unclear. Following CAC induction in wild-type (WT) and STAT6-deficient mice (STAT6^-/-), we found that 70% of STAT6^-/- mice were tumor-free after 8 weeks, whereas 100% of WT mice developed tumors. STAT6^-/- mice displayed fewer and smaller colorectal tumors than WT mice; this reduced tumorigenicity was associated with decreased proliferation and increased apoptosis in the colonic mucosa in the early steps of tumor progression. STAT6^-/- mice also exhibited reduced inflammation, diminished concentrations COX2 and nuclear β-catenin protein in the colon, and decreased mRNA expression of IL17A and TNFα, but increased IL10 expression when compared with WT mice. Impaired mucosal expression of CCL9, CCL25, and CXCR2 was also observed. In addition, the number of circulating CD11b⁺Ly6C^hiCCR2⁺ monocytes and CD11b⁺Ly6C^lowLy6G⁺ granulocytes was both decreased in a STAT6-dependent manner. Finally, WT mice receiving a STAT6 inhibitor in vivo confirmed a significant reduction in tumor load as well as less intense signs of CAC. Our results demonstrate that STAT6 is critical in the early steps of CAC development for modulating inflammatory responses and controlling cell recruitment and proliferation. Thus, STAT6 may represent a promising target for CAC treatment. Cancer Immunol Res; 5(5); 385-96. ©2017 AACR.

Interleukin-4 Inhibits Regulatory T Cell Differentiation through Regulating CD103+ Dendritic Cells

CD103+ dendritic cells (DCs) have been shown to play a crucial role in the pathogenesis of inflammatory bowel diseases (IBDs) through educating regulatory T (Treg) cells differentiation. However, the mechanism of CD103+ DCs subsets differentiation remains elusive. Interleukin (IL)-4 is a pleiotropic cytokine that is upregulated in certain types of inflammation, including IBDs and especially ulcerative colitis. However, the precise role of IL-4 in the differentiation of CD103+ DCs subpopulation remains unknown. In this study, we observed a repressive role of IL-4 on the CD103+ DCs differentiation in both mouse and human. High-dose IL-4 inhibited the CD103+ DC differentiation. In comparison to CD103- DCs, CD103+ DCs expressed high levels of the co-stimulatory molecules and indoleamine 2,3-dioxygenase (IDO). Interestingly, IL-4 diminished IDO expression on DCs in a dose-dependent manner. Besides, high-dose IL-4-induced bone marrow-derived DCs, and monocyte-derived DCs revealed mature DCs profiles, characterized by increased co-stimulatory molecules and decreased pinocytotic function. Furthermore, DCs generated under low concentrations of IL-4 favored Treg cells differentiation, which depend on IDO produced by CD103+ DCs. Consistently, IL-4 also reduced the frequency of CD103+ DC in vivo. Thus, we here demonstrated that the cytokine IL-4 involved in certain types of inflammatory diseases by orchestrating the functional phenotype of CD103+ DCs subsets.

Gut permeability and mucosal inflammation: bad, good or context dependent

Inflammatory bowel disease (IBD) is a multifactorial disease. A breach in the mucosal barrier, otherwise known as "leaky gut," is alleged to promote mucosal inflammation by intensifying immune activation. However, interaction between the luminal antigen and mucosal immune system is necessary to maintain mucosal homeostasis. Furthermore, manipulations leading to deregulated gut permeability have resulted in susceptibility in mice to colitis as well as to creating adaptive immunity. These findings implicate a complex but dynamic association between mucosal permeability and immune homeostasis; however, they also emphasize that compromised gut permeability alone may not be sufficient to induce colitis. Emerging evidence further supports the role(s) of proteins associated with the mucosal barrier in epithelial injury and repair: manipulations of associated proteins also modified epithelial differentiation, proliferation, and apoptosis. Taken together, the role of gut permeability and proteins associated in regulating mucosal inflammatory diseases appears to be more complex than previously thought. Herein, we review outcomes from recent mouse models where gut permeability was altered by direct and indirect effects of manipulating mucosal barrier-associated proteins, to highlight the significance of mucosal permeability and the non-barrier-related roles of these proteins in regulating chronic mucosal inflammatory conditions.

A Single Species of Clostridium Subcluster XIVa Decreased in Ulcerative Colitis Patients

BACKGROUND

Imbalance of the intestinal microbiota is associated with gastrointestinal disease and autoimmune disease and metabolic syndrome. Analysis of the intestinal microbiota has recently progressed, and the association with inflammatory bowel disease has been reported at the species level. Such findings suggest that the recovery of homeostasis in the intestinal microbiota could cure inflammatory bowel disease. We aimed to search new probiotic candidates for inflammatory bowel disease through translational research by analysis of ulcerative colitis (UC) patients' intestinal microbiota and clarify the effects of them on inflammation. Here, we focused on Fusicatenibacter saccharivorans, which belongs to Clostridium subcluster XIVa and was successfully isolated and cultured in 2013. We analyzed the association of F. saccharivorans to UC patients' activity and inflammation for the first time.

METHODS

Feces from UC patients and healthy controls were analyzed by 16S ribosomal RNA gene sequences. F. saccharivorans was administered to murine colitis model. Colitic lamina propria mononuclear cells from UC patients and mice were stimulated with F. saccharivorans.

RESULTS

The whole fecal bacteria in active UC patients were less than that in quiescent UC patients. Furthermore, F. saccharivorans was decreased in active UC patients and increased in quiescent. The administration of F. saccharivorans improved murine colitis. F. saccharivorans induced interleukin 10 production by lamina propria mononuclear cells from not only colitis model mice but also UC patients.

CONCLUSIONS

F. saccharivorans decreased in correlation to UC activity and suppresses intestinal inflammation. These results suggest that F. saccharivorans could lead to a novel UC treatment.

The L-Arginine Transporter Solute Carrier Family 7 Member 2 Mediates the Immunopathogenesis of Attaching and Effacing Bacteria

Solute carrier family 7 member 2 (SLC7A2) is an inducible transporter of the semi-essential amino acid L-arginine (L-Arg), which has been implicated in immune responses to pathogens. We assessed the role of SLC7A2 in murine infection with Citrobacter rodentium, an attaching and effacing enteric pathogen that causes colitis. Induction of SLC7A2 was upregulated in colitis tissues, and localized predominantly to colonic epithelial cells. Compared to wild-type mice, Slc7a2^–/–mice infected with C. rodentium had improved survival and decreased weight loss, colon weight, and histologic injury; this was associated with decreased colonic macrophages, dendritic cells, granulocytes, and Th1 and Th17 cells. In infected Slc7a2^–/–mice, there were decreased levels of the proinflammatory cytokines G-CSF, TNF-α, IL-1α, IL-1β, and the chemokines CXCL1, CCL2, CCL3, CCL4, CXCL2, and CCL5. In bone marrow chimeras, the recipient genotype drove the colitis phenotype, indicative of the importance of epithelial, rather than myeloid SLC7A2. Mice lacking Slc7a2 exhibited reduced adherence of C. rodentium to the colonic epithelium and decreased expression of Talin-1, a focal adhesion protein involved in the attachment of the bacterium. The importance of SLC7A2 and Talin-1 in the intimate attachment of C. rodentium and induction of inflammatory response was confirmed in vitro, using conditionally-immortalized young adult mouse colon (YAMC) cells with shRNA knockdown of Slc7a2 or Tln1. Inhibition of L-Arg uptake with the competitive inhibitor, L-lysine (L-Lys), also prevented attachment of C. rodentium and chemokine expression. L-Lys and siRNA knockdown confirmed the role of L-Arg and SLC7A2 in human Caco-2 cells co-cultured with enteropathogenic Escherichia coli. Overexpression of SLC7A2 in human embryonic kidney cells increased bacterial adherence and chemokine expression. Taken together, our data indicate that C. rodentium enhances its own pathogenicity by inducing the expression of SLC7A2 to favor its attachment to the epithelium and thus create its ecological niche.

Intestinal infections by attaching and effacing (A/E) bacteria widely impact human health, with major social and economic repercussions. Mucosal immunity plays a critical role in determining the outcome of these infections. The amino acid L-arginine regulates inflammatory responses to bacterial pathogens. We studied the role of the L-arginine transporter solute carrier family 7 member 2 (SLC7A2) during infection with the A/E pathogen Citrobacter rodentium. SLC7A2 is induced in colonic epithelial cells during the infection and facilitates the intimate attachment of the bacteria, thus initiating the inflammatory response of the infected mucosa. These data were confirmed in vitro using C. rodentium-infected mouse cells and human colonic epithelial cells infected with enteropathogenic Escherichia coli. Our work describes a mechanism by which A/E bacteria manipulate host response to favor their colonization, thereby positioning SLC7A2 as an unrecognized therapeutic target to limit infection with enterobacteria.

The activation of Wnt signaling by a STAT6-dependent macrophage phenotype promotes mucosal repair in murine IBD

The complete repair of the mucosa constitutes a key goal in inflammatory bowel disease (IBD) treatment. The Wnt signaling pathway mediates mucosal repair and M2 macrophages that coordinate efficient healing have been related to Wnt ligand expression. Signal transducer and activator of transcription 6 (STAT6) mediates M2 polarization in vitro and we hypothesize that a STAT6-dependent macrophage phenotype mediates mucosal repair in acute murine colitis by activating the Wnt signaling pathway. Our results reveal an impaired mucosal expression of M2 macrophage-associated genes and delayed wound healing in STAT6(-/-) mice treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS). These mice also exhibited decreased mucosal expression of Wnt2b, Wnt7b, and Wnt10a, diminished protein levels of nuclear β-catenin that is mainly located in crypts adjacent to damage, and reduced mRNA expression of two Wnt/β-catenin target molecules Lgr5 and c-Myc when compared with wild-type (WT) mice. Murine peritoneal macrophages treated with interleukin-4 (IL-4) and polarized toward an M2a phenotype overexpressed Wnt2b, Wnt7b, and Wnt10a in a STAT6-dependent manner. Administration of a Wnt agonist as well as transfer of properly polarized M2a macrophages to STAT6(-/-) mice activated the Wnt signaling pathway in the damaged mucosa and accelerated wound healing. Our results demonstrate that a STAT6-dependent macrophage phenotype promotes mucosal repair in TNBS-treated mice through activation of the Wnt signaling pathway.

Cytokine Networks and T-Cell Subsets in Inflammatory Bowel Diseases

Pathogenesis of the inflammatory bowel diseases (IBDs), such as ulcerative colitis (UC) and Crohn's disease (CD), involve proinflammatory changes within the microbiota, chronic immune-mediated inflammatory responses, and epithelial dysfunction. Converging data from genome-wide association studies, mouse models of IBD, and clinical trials indicate that cytokines are key effectors of both normal homeostasis and chronic inflammation in the gut. Yet many questions remain concerning the role of specific cytokines in different IBDs within distinct regions of the gut, and regarding cellular mechanisms of action. In this article, we review current and emerging concepts concerning the role of cytokines in IBD with a focus on immune regulation, T cell subsets, and potential clinical applications.