DR3 Regulates Intestinal Epithelial Homeostasis and Regeneration After Intestinal Barrier Injury

BACKGROUND & AIMS

Tumor necrosis factor (TNF) superfamily member tumor necrosis factor-like protein 1A (TL1A) has been associated with the susceptibility and severity of inflammatory bowel diseases. However, the function of the tumor necrosis factor-like protein 1A and its receptor death receptor 3 (DR3) in the development of intestinal inflammation is incompletely understood. We investigated the role of DR3 expressed by intestinal epithelial cells (IECs) during intestinal homeostasis, tissue injury, and regeneration.

METHODS

Clinical phenotype and histologic inflammation were assessed in C57BL/6 (wild-type), Tl1a-/- and Dr3-/- mice in dextran sulfate sodium (DSS)-induced colitis. We generated mice with an IEC-specific deletion of DR3 (Dr3ΔIEC) and assessed intestinal inflammation and epithelial barrier repair. In vivo intestinal permeability was assessed by fluorescein isothiocyanate dextran uptake. Proliferation of IECs was analyzed by bromodeoxyuridine incorporation. Expression of DR3 messenger RNA was assessed by fluorescent in situ hybridization. Small intestinal organoids were used to determine ex vivo regenerative potential.

RESULTS

Dr3-/- mice developed more severe colonic inflammation than wild-type mice in DSS-induced colitis with significantly impaired IEC regeneration. Homeostatic proliferation of IECs was increased in Dr3-/- mice, but blunted during regeneration. Cellular localization and expression of the tight junction proteins Claudin-1 and zonula occludens-1 were altered, leading to increased homeostatic intestinal permeability. Dr3ΔIEC mice recapitulated the phenotype observed in Dr3-/- mice with increased intestinal permeability and IEC proliferation under homeostatic conditions and impaired tissue repair and increased bacterial translocation during DSS-induced colitis. Impaired regenerative potential and altered zonula occludens-1 localization also were observed in Dr3ΔIEC enteroids.

CONCLUSIONS

Our findings establish a novel function of DR3 in IEC homeostasis and postinjury regeneration independent of its established role in innate lymphoid cells and T-helper cells.

Elafin Reverses Intestinal Fibrosis by Inhibiting Cathepsin S-Mediated Protease-Activated Receptor 2

BACKGROUND & AIMS

More than half of Crohn's disease patients develop intestinal fibrosis-induced intestinal strictures. Elafin is a human protease inhibitor that is down-regulated in the stricturing intestine of Crohn's disease patients. We investigated the efficacy of elafin in reversing intestinal fibrosis and elucidated its mechanism of action.

METHODS

We developed a new method to mimic a stricturing Crohn's disease environment and induce fibrogenesis using stricturing Crohn's disease patient-derived serum exosomes to condition fresh human intestinal tissues and primary stricturing Crohn's disease patient-derived intestinal fibroblasts. Three mouse models of intestinal fibrosis, including SAMP1/YitFc mice, Salmonella-infected mice, and trinitrobenzene sulfonic acid-treated mice, were also studied. Elafin-Eudragit FS30D formulation and elafin-overexpressing construct and lentivirus were used.

RESULTS

Elafin reversed collagen synthesis in human intestinal tissues and fibroblasts pretreated with Crohn's disease patient-derived serum exosomes. Proteome arrays identified cathepsin S as a novel fibroblast-derived pro-fibrogenic protease. Elafin directly suppressed cathepsin S activity to inhibit protease-activated receptor 2 activity and Zinc finger E-box-binding homeobox 1 expression, leading to reduced collagen expression in intestinal fibroblasts. Elafin overexpression reversed ileal fibrosis in SAMP1/YitFc mice, cecal fibrosis in Salmonella-infected mice, and colonic fibrosis in trinitrobenzene sulfonic acid-treated mice. Cathepsin S, protease-activated receptor 2 agonist, and zinc finger E-box-binding homeobox 1 overexpression abolished the anti-fibrogenic effect of elafin in fibroblasts and all 3 mouse models of intestinal fibrosis. Oral elafin-Eudragit FS30D treatment abolished colonic fibrosis in trinitrobenzene sulfonic acid-treated mice.

CONCLUSIONS

Elafin suppresses collagen synthesis in intestinal fibroblasts via cathepsin S-dependent protease-activated receptor 2 inhibition and decreases zinc finger E-box-binding homeobox 1 expression. The reduced collagen synthesis leads to the reversal of intestinal fibrosis. Thus, modified elafin may be a therapeutic approach for intestinal fibrosis.

TNF-Like Ligand 1 Aberrance Aggravates Nonalcoholic Steatohepatitis via M1 Macrophage Polarization

Nonalcoholic steatohepatitis (NASH) is a progressive, chronic liver disease worldwide which imposes a large economic burden on society. M1/M2 macrophage balance destruction and recruitment of mononuclear immune cells to the liver play critical roles in NASH. Several studies have shown that the expression of TNF-like ligand 1 aberrance (TL1A) increased in macrophages associated with many inflammatory diseases, for example, inflammatory bowel disease, primary biliary cholangitis, and liver fibrosis. One recent research showed that weight, abdominal adipose, and liver leptin, one of the critical fat cytokines, were reduced in TL1A knockout mice. However, the functional and molecular regulatory mechanisms of TL1A on macrophage polarization and recruitment in NASH have yet to be clarified. The authors found that high fructose high fat diet and methionine-choline deficiency diet induced the expression of TL1A in macrophages of liver tissue from murine NASH models. Myeloid-specific TL1A overexpressed mice showed exacerbated steatohepatitis with increased hepatic lipid accumulation, inflammation, liver injury, and apoptosis. M1 macrophages' infiltration and the production of proinflammatory and chemotactic cytokines increased in liver of NASH mouse models with myeloid-specific TL1A overexpressed. Furthermore, this paper revealed that bone marrow-derived macrophages and Kupffer cells with overexpression of TL1A exacerbated the lipid accumulation and expression of proinflammatory factors in the murine primary hepatocytes after free fatty acid treatment in vitro. In conclusion, TL1A-mediated M1-type macrophage polarization and recruitment into the liver promoted steatohepatitis in murine NASH.

Effect and Mechanism of TL1A Expression on Epithelial-Mesenchymal Transition during Chronic Colitis-Related Intestinal Fibrosis

BACKGROUND AND AIMS

Recent evidences reveal that epithelial to mesenchymal transition (EMT) exacerbates the process of intestinal fibrosis. Tumor necrosis factor-like ligand 1A (TL1A) is a member of the tumor necrosis family (TNF), which can take part in the development of colonic inflammation and fibrosis by regulating immune response or inflammatory factors. The purpose of this study was to elucidate the possible contribution of TL1A in onset and progression of intestinal inflammation and fibrosis through EMT.

METHODS

Colonic specimens were obtained from patients with inflammatory bowel disease (IBD) and control individuals. The expression levels of TL1A and EMT-related markers in intestinal tissues were evaluated. Furthermore, the human colorectal adenocarcinoma cell line, HT-29, was stimulated with TL1A, anti-TL1A antibody, or BMP-7 to assess EMT process. In addition, transgenic mice expressing high levels of TL1A in lymphoid cells were used to further investigate the mechanism of TL1A in intestinal fibrosis.

RESULTS

High levels of TL1A expression were detected in the intestinal specimens of patients with ulcerative colitis and Crohn's disease and were negatively associated with the expression of an epithelial marker (E-cadherin), while it was positively associated with the expression of interstitial markers (FSP1 and α-SMA). Transgenic mice with high expression of TL1A were more sensitive to dextran sodium sulfate and exhibited severe intestinal inflammation and fibrosis. Additionally, the TGF-β1/Smad3 pathway may be involved in TL1A-induced EMT, and the expression of IL-13 and EMT-related transcriptional molecules (e.g., ZEB1 and Snail1) was increased in the intestinal specimens of the transgenic mice. Furthermore, TL1A-induced EMT can be influenced by anti-TL1A antibody or BMP-7 in vitro.

CONCLUSIONS

TL1A participates in the formation and process of EMT in intestinal fibrosis. This new knowledge enables us to better understand the pathogenesis of intestinal fibrosis and identify new therapeutic targets for its treatment.

TL1A primed dendritic cells activation exacerbated chronic murine colitis

AIMS

Tumor necrosis factor-like ligand 1A (TL1A) has been proved to activate adaptive immunity in inflammatory bowel disease (IBD). However, its role in the regulation of intestinal dendritic cells (DCs) has not been fully characterized. This study aims to investigate the modulation of TL1A in DCs activation in murine colitis.

MATERIALS AND METHODS

Myeloid TL1A-Transgenic C57BL/6 mice and wild-type (WT) mice were administrated with dextran sulfate sodium (DSS) to explore the effects of TL1A in murine colitis. Bone marrow-derived DCs (BMDCs) were isolated to detect the ability of antigen phagocytosis and presentation. The expression of nuclear factor-κB (NF-κB) pathway and chemokines receptors (CCRs) was assessed by real-time PCR and Western blot.

KEY FINDINGS

Myeloid cells with constitutive TL1A expression developed worsened murine colitis with exacerbated T_H1/T_H17 cytokine responses. Intestinal DCs from TL1A transgenic mice expressed high levels of costimulatory molecules (CD80 and CD86) with increased pro-inflammatory cytokines of IL-1β, TNF-α and IL-12/23 p40. Mechanistic studies showed that TL1A enhanced the phagocytotic ability of BMDCs. Moreover, TL1A enhanced the capacity of antigen process and presentation in BMDCs. Besides, TL1A induced the phosphorylation of NF-κB(p65) and IκBα. Meanwhile, higher expression of CCR2, CCR5, CCR7, and CX3CR1 was observed both in vivo and in vitro.

SIGNIFICANCE

TL1A exacerbated DSS-induced chronic experimental colitis, probably through activation and migration of dendritic cells, and therefore increasing the secretion of pro-inflammatory cytokines.

Direct signaling of TL1A-DR3 on fibroblasts induces intestinal fibrosis in vivo

Tumor necrosis factor-like cytokine 1A (TL1A, TNFSF15) is implicated in inflammatory bowel disease, modulating the location and severity of inflammation and fibrosis. TL1A expression is increased in inflamed mucosa and associated with fibrostenosing Crohn's disease. Tl1a-overexpression in mice causes spontaneous ileitis, and exacerbates induced proximal colitis and fibrosis. Intestinal fibroblasts express Death-receptor 3 (DR3; the only know receptor for TL1A) and stimulation with TL1A induces activation in vitro. However, the contribution of direct TL1A-DR3 activation on fibroblasts to fibrosis in vivo remains unknown. TL1A overexpressing naïve T cells were transferred into Rag-/- , Rag-/- mice lacking DR3 in all cell types (Rag-/-Dr3-/-), or Rag-/- mice lacking DR3 only on fibroblasts (Rag-/-Dr3∆Col1a2) to induce colitis and fibrosis, assessed by clinical disease activity index, intestinal inflammation, and collagen deposition. Rag-/- mice developed overt colitis with intestinal fibrostenosis. In contrast, Rag-/-Dr3-/- demonstrated decreased inflammation and fibrosis. Despite similar clinical disease and inflammation as Rag-/-, Rag-/-Dr3∆Col1a2 exhibited reduced intestinal fibrosis and attenuated fibroblast activation and migration. RNA-Sequencing of TL1A-stimulated fibroblasts identified Rho signal transduction as a major pathway activated by TL1A and inhibition of this pathway modulated TL1A-mediated fibroblast functions. Thus, direct TL1A signaling on fibroblasts promotes intestinal fibrosis in vivo. These results provide novel insight into profibrotic pathways mediated by TL1A paralleling its pro-inflammatory effects.

Gut microbial transcytosis induced by tumor necrosis factor-like 1A-dependent activation of a myosin light chain kinase splice variant contributes to IBD

Inflammatory bowel disease (IBD) is characterized by abnormal host-microbe interactions. Proinflammatory cytokine IFNγ and a novel TNF superfamily member, TL1A, have been implicated in epithelial barrier dysfunction. The divergent regulatory mechanisms of transcellular versus paracellular hyperpermeability remain poorly understood. Intestinal epithelia express two splice variants of long myosin light chain kinase (MLCK), of which the full-length MLCK1 differ from the shorter isoform MLCK2 by a Src kinase phosphorylation site. The aim was to investigate the roles of MLCK splice variants in gut barrier defects under proinflammatory stress. Upregulated expression of TL1A, IFNγ, and two MLCK variants was observed in human IBD biopsy specimens. The presence of intraepithelial bacteria preceded tight junction (TJ) damage in dextran sodium sulfate-treated and TL1A-transgenic mouse models. Lack of barrier defects was observed in long MLCK(-/-) mice. TL1A induced MLCK-dependent terminal web (TW) contraction, brush border fanning, and transepithelial bacterial internalization. The bacterial taxa identified in the inflamed colonocytes included Escherichia, Enterococcus, Staphylococcus,and Lactobacillus. Recombinant TL1A and IFNγ at low doses induced PI3K/Akt/MLCK2-dependent bacterial endocytosis, whereas high-dose IFNγ caused TJ opening via the iNOS/Src/MLCK1 axis. Bacterial internalization was recapitulated in MLCK-knockout cells individually expressing MLCK2 but not MLCK1. Immunostaining showed different subcellular sites of phosphorylated MLC localized to the TJ and TW in the MLCK1- and MLCK2-expressing cells, respectively. In conclusion, proinflammatory cytokines induced bacterial influx through transcellular and paracellular routes via divergent pathways orchestrated by distinct MLCK isoforms. Bacterial transcytosis induced by TL1A may be an alternative route causing symptom flares in IBD.

Epithelial endoplasmic reticulum stress orchestrates a protective IgA response

Immunoglobulin A (IgA) is the major secretory immunoglobulin isotype found at mucosal surfaces, where it regulates microbial commensalism and excludes luminal factors from contacting intestinal epithelial cells (IECs). IgA is induced by both T cell-dependent and -independent (TI) pathways. However, little is known about TI regulation. We report that IEC endoplasmic reticulum (ER) stress induces a polyreactive IgA response, which is protective against enteric inflammation. IEC ER stress causes TI and microbiota-independent expansion and activation of peritoneal B1b cells, which culminates in increased lamina propria and luminal IgA. Increased numbers of IgA-producing plasma cells were observed in healthy humans with defective autophagy, who are known to exhibit IEC ER stress. Upon ER stress, IECs communicate signals to the peritoneum that induce a barrier-protective TI IgA response.

Effects and Mechanism of Constitutive TL1A Expression on Intestinal Mucosal Barrier in DSS-Induced Colitis

OBJECTIVE

The role of TL1A in the intestinal mucosa barrier in inflammatory bowel disease (IBD) is still unclear. This study was aimed to investigate the expression levels of tight junction protein (TJ), myosin light chain kinase (MLCK), MyD88 and tumor necrosis factor (TNF) receptor-associated factor-6 (TRAF6) and how TL1A influences the intestinal barrier in IBD.

METHODS

The mouse models of IBD were built using FMS-TL1A-GFP-transgenic mice and wild-type mice. The morphological and histopathological changes, bacterial translocation, permeability of colonic mucosa, and LPS level were assessed. Caco-2 cells were used to further investigate the association between TL1A and TNF-α and LPS. The protein level and mRNA changes of TJ proteins including ZO-1, occluding, JAMA, claudin-1, claudin-2, and claudin-3 were investigated using Western blot and real-time PCR. Protein changes of MLCK, MyD88 and TNF receptor-associated factor-6 (TRAF6), and TNF-α mRNA in the mouse colon were further assessed.

RESULTS

The IBD models were successfully built. Cooper HS score and histopathological score of the colon were higher in DSS/WT group than in control/WT group (P < 0.05), higher in DSS/Tg group than in control/Tg group (P < 0.05), and higher in DSS/Tg group than in DSS/WT group. PAS, colonic permeability of the colon, and FITC-D examination showed the similar results and trends. Compared with control/WT group, the levels of TL1A and claudin-2 were higher and the levels of ZO-1, occludin, JAMA, claudin-1, and claudin-3 were lower in DSS/WT group (P < 0.05). Compared with control/Tg group, the levels of TL1A and claudin-2 were higher and the levels of ZO-1, occludin, JAMA, claudin-1, and claudin-3 were lower in DSS/Tg group. Compared with Caco-2 + TNF-α group, the expression level of occludin and claudin-1 in Caco-2 + LV-TNFSF15 + TNF-α group was significantly lower (P < 0.05); p-MLC level was significantly higher. Compared with Caco-2 + LPS group, the expression level of occludin and claudin-1 significantly decreased in Caco-2 + LV-TNFSF15 + LPS group; MyD88 and TRAF6 expression level significantly increased.

CONCLUSION

The results suggested that TL1A could impair intestinal epithelial barrier in the mouse model of IBD and might regulate TJ expression via MLCK/p-MLC pathway and LPS-mediated MyD88/TRAF6 pathway.

Microbiota-Induced TNF-like Ligand 1A Drives Group 3 Innate Lymphoid Cell-Mediated Barrier Protection and Intestinal T Cell Activation during Colitis

Inflammatory bowel disease (IBD) results from a dysregulated interaction between the microbiota and a genetically susceptible host. Genetic studies have linked TNFSF15 polymorphisms and its protein TNF-like ligand 1A (TL1A) with IBD, but the functional role of TL1A is not known. Here, we found that adherent IBD-associated microbiota induced TL1A release from CX3CR1+ mononuclear phagocytes (MNPs). Using cell-specific genetic deletion models, we identified an essential role for CX3CR1+MNP-derived TL1A in driving group 3 innate lymphoid cell (ILC3) production of interleukin-22 and mucosal healing during acute colitis. In contrast to this protective role in acute colitis, TL1A-dependent expression of co-stimulatory molecule OX40L in MHCII+ ILC3s during colitis led to co-stimulation of antigen-specific T cells that was required for chronic T cell colitis. These results identify a role for ILC3s in activating intestinal T cells and reveal a central role for TL1A in promoting ILC3 barrier immunity during colitis.

Fecal Microbiota Transplantation in Inflammatory Bowel Disease: A Primer for Internists

Inflammatory bowel disease consists of disorders characterized by chronic idiopathic bowel inflammation. The concept of host-gut-microbiome interaction in the pathogenesis of various complex immune-mediated chronic diseases, including inflammatory bowel disease, has recently generated immense interest. Mounting evidence confirms alteration of intestinal microflora in patients with inflammatory bowel disease. Thus, restoration of normal gut microbiota has become a focus of basic and clinical research in recent years. Fecal microbiota transplantation is being explored as one such therapeutic strategy and has shown encouraging results in the management of patients with inflammatory bowel disease.

Mesenchymal stem cell transplantation improves chronic colitis-associated complications through inhibiting the activity of toll-like receptor-4 in mice

Background

A variety of extra-intestinal manifestations (EIMs), including hepatobiliary complications, are associated with inflammatory bowel disease (IBD). Mesenchymal stem cells (MSCs) have been shown to play a potential role in the therapy of IBD. This study was designed to investigate the effect and mechanism of MSCs on chronic colitis-associated hepatobiliary complications using mouse chronic colitis models induced by dextran sulfate sodium (DSS).

Methods

DSS-induced mouse chronic colitis models were established and treated with MSCs. Severity of colitis was evaluated by disease activity index (DAI), body weight (BW), colon length and histopathology. Serum lipopolysaccharide (LPS) levels were detected by limulus amebocyte lysate test (LAL-test). Histology and liver function of the mice were checked correspondingly. Serum LPS levels and bacterial translocation of mesenteric lymph nodes (MLN) were detected. Pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-17A (IL-17A), Toll receptor 4 (TLR4), TNF receptor-associated factor 6 (TRAF6) and nuclear factor kappa B (NF-κB) were detected by immunohistochemical staining, western blot analysis and real-time PCR, respectively.

Results

The DSS-induced chronic colitis model was characterized by reduced BW, high DAI, worsened histologic inflammation, and high levels of LPS and E. coli. Liver histopathological lesions, impaired liver function, enhanced proteins and mRNA levels of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB were observed after DSS administration. MSCs transplantation markedly ameliorated the pathology of colon and liver by reduction of LPS levels and proteins and mRNA expressions of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB.

Conclusions

MSCs can improve chronic colitis-associated hepatobiliary complications, probably by inhibition of enterogenous endotoxemia and hepatic inflammation through LPS/TLR4 pathway. MSCs may represent a novel therapeutic approach for chronic colitis-associated hepatobiliary complications.

Mesenteric Adipose-derived Stromal Cells From Crohn's Disease Patients Induce Protective Effects in Colonic Epithelial Cells and Mice With Colitis

Mesenteric adipose tissue hyperplasia is a hallmark of Crohn's disease (CD). Recently, we showed that mesenteric adipose-derived stromal cells (ADSCs) from CD, ulcerative colitis, and control patients synthesize and release adipokines in a disease-dependent manner. Here we examined the expression profiles of CD and control patient-derived mesenteric ADSCs and studied the effects of their extracellular mediators on colonocyte signaling in vitro and experimental colitis in vivo. ADSCs were isolated from mesenteric fat of control and CD patients. Microarray profiling and network analysis were performed in ADSCs and human colonocytes treated with conditioned media from cultured ADSCs. Mice with acute colitis received daily injections of conditioned media from patient-derived ADSCs, vehicle, or apolactoferrin. Proliferative responses were evaluated in conditioned media-treated colonocytes and mouse colonic epithelium. Total protein was isolated from cultured colonocytes after treatment with apolactoferrin for Western blot analysis of phosphorylated intracellular signaling kinases. Microarray profiling revealed differential mRNA expression in CD patient-derived ADSCs compared with controls, including lactoferrin. Administration of CD patient-derived medium or apolactoferrin increased colonocyte proliferation compared with controls. Conditioned media from CD patient-derived ADSCs or apolactoferrin attenuated colitis severity in mice and enhanced colonocyte proliferation in vivo. ADSCs from control and CD patients show disease-dependent inflammatory responses and alter colonic epithelial cell signaling in vitro and in vivo. Furthermore, we demonstrate lactoferrin production by adipose tissue, specifically mesenteric ADSCs. We suggest that mesenteric ADSC-derived lactoferrin may mediate protective effects and participate in the pathophysiology of CD by promoting colonocyte proliferation and the resolution of inflammation.

Serological, genetic and clinical associations with increased health-care resource utilization in inflammatory bowel disease

OBJECTIVE

Inflammatory bowel diseases (IBD) are associated with significant morbidity and economic burden. The variable course of IBD creates a need for predictors of clinical outcomes and health resource utilization (HRU) to guide treatment decisions. We aimed to identify clinical, serological or genetic markers associated with inpatient resource utilization in patients with ulcerative colitis (UC) and Crohn's disease (CD).

METHODS

Patients with IBD with available genetic and serological data who had at least one emergency department visit or hospitalization in a 3-year period were included. The primary outcome measure was HRU, as measured by the All Patient Refined Diagnosis Related Group classification system. Univariate and multivariate linear and logistic regression models were used to identify the associations with HRU.

RESULTS

Altogether 858 (562 CD and 296 UC) patients were included. Anti-CBir1 seropositivity (P = 0.002, effect size [ES]: 0.762, 95% confidence interval [CI] 0.512-1.012) and low socioeconomic status (P = 0.005, ES: 1.620 [95% CI 1.091-2.149]) were independently associated with a high HRU. CD diagnosis (P = 0.006, ES: -0.701 [95% CI -0.959 to -0.443]) was independently associated with a low inpatient HRU.

CONCLUSION

In patients with IBD who required at least one emergency department visit or hospitalization, anti-CBir1 antibody status may be a useful biomarker of HRU when formulating management strategies to reduce disease complications and resource utilization.

CSA13 inhibits colitis-associated intestinal fibrosis via a formyl peptide receptor like-1 mediated HMG-CoA reductase pathway

Many Crohn’s disease (CD) patients develop intestinal strictures, which are difficult to prevent and treat. Cationic steroid antimicrobial 13 (CSA13) shares cationic nature and antimicrobial function with antimicrobial peptide cathelicidin. As many functions of cathelicidin are mediated through formyl peptide receptor-like 1 (FPRL1), we hypothesize that CSA13 mediates anti-fibrogenic effects via FPRL1. Human intestinal biopsies were used in clinical data analysis. Chronic trinitrobenzene sulfonic acid (TNBS) colitis-associated intestinal fibrosis mouse model with the administration of CSA13 was used. Colonic FPRL1 mRNA expression was positively correlated with the histology scores of inflammatory bowel disease patients. In CD patients, colonic FPRL1 mRNA was positively correlated with intestinal stricture. CSA13 administration ameliorated intestinal fibrosis without influencing intestinal microbiota. Inhibition of FPRL1, but not suppression of intestinal microbiota, reversed these protective effects of CSA13. Metabolomic analysis indicated increased fecal mevalonate levels in the TNBS-treated mice, which were reduced by the CSA13 administration. CSA13 inhibited colonic HMG-CoA reductase activity in an FPRL1-dependent manner. Mevalonate reversed the anti-fibrogenic effect of CSA13. The increased colonic FPRL1 expression is associated with severe mucosal disease activity and intestinal stricture. CSA13 inhibits intestinal fibrosis via FPRL1-dependent modulation of HMG-CoA reductase pathway.

TL1A blocking ameliorates intestinal fibrosis in the T cell transfer model of chronic colitis in mice

Tumor necrosis factor like cytokine 1A (TL1A) is a member of the TNF superfamily. Accumulating evidence demonstrated the importance of TL1A in the pathogenesis of inflammatory bowel disease (IBD) and suggested a potential role of TL1A blocking in IBD therapy. Here we aimed to explore whether the anti-TL1A antibody could ameliorate intestinal inflammation and fibrosis in IBD. A T cell transfer model of chronic colitis was induced by intraperitoneal injection of CD4⁺CD45RB^high naive T cells isolated from either C57BL/6 wild type (WT) mice or LCK-CD2-Tl1a-GFP transgenic (L-Tg) mice into recombinase activating gene-1-deficient (RAG^-/-) mice. The colitis model mice were treated prophylactically or therapeutically with anti-Tl1a antibody or IgG isotype control. Haematoxylin and eosin staining (H&E staining), Masson's trichrome staining (MT staining) and sirius red staining were used to detect histopathological changes in colonic tissue; immunohistochemical staining was used to detect the expressions of collagen I, collagen III, TIMP1, vimentin, α-SMA and TGF-β1/Smad3. Results showed that anti-Tl1a antibody could reduce intestinal inflammation and fibrosis by inhibiting the activation of intestinal fibroblasts and reducing the collagen synthesis in the T cell transfer model of chronic colitis. The mechanism may be related to the inhibition of TGF-1/Smad3 signaling pathway.

Insights on the use of biosimilars in the treatment of inflammatory bowel disease

Biologic therapy, such as those that target tumor necrosis factor (TNF) signaling, has proven to be an efficacious method of treatment for patients with inflammatory bowel disease (IBD) with regards to symptom management and mucosal healing. However, the rising prevalence of IBD worldwide and the ever-increasing burden of biologic pharmaceuticals in the health care industry is alarming for insurance companies, clinicians, and patients. The impending patent expiry and the relatively high costs of biologics, particularly anti-TNF agents, have paved the way for biosimilar development for IBD. The United States Food and Drug Administration defines a biosimilar as a biological product that is highly similar to its reference medicinal product, with no clinically meaningful differences in terms of safety, purity, and potency. The hope with biosimilars is that their entry into the market will be able to drive competition between pharmaceutical companies to reduce prices like that of the generic market, and that access to appropriate biologic treatments for IBD patients is increased in the long-term. Yet, there are challenging issues such as indication extrapolation and interchangeability that are still being debated in the field of IBD and must be addressed in future issued guidance. This review will discuss the issues and implications concerning the use of biosimilar therapy for IBD.

Defective ATG16L1-mediated removal of IRE1α drives Crohn's disease-like ileitis

ATG16L1^T300A, a major risk polymorphism in Crohn's disease (CD), causes impaired autophagy, but it has remained unclear how this predisposes to CD. In this study, we report that mice with Atg16l1 deletion in intestinal epithelial cells (IECs) spontaneously develop transmural ileitis phenocopying ileal CD in an age-dependent manner, driven by the endoplasmic reticulum (ER) stress sensor IRE1α. IRE1α accumulates in Paneth cells of Atg16l1^ΔIEC mice, and humans homozygous for ATG16L1^T300A exhibit a corresponding increase of IRE1α in intestinal epithelial crypts. In contrast to a protective role of the IRE1β isoform, hyperactivated IRE1α also drives a similar ileitis developing earlier in life in Atg16l1;Xbp1^ΔIEC mice, in which ER stress is induced by deletion of the unfolded protein response transcription factor XBP1. The selective autophagy receptor optineurin interacts with IRE1α, and optineurin deficiency amplifies IRE1α levels during ER stress. Furthermore, although dysbiosis of the ileal microbiota is present in Atg16l1;Xbp1^ΔIEC mice as predicted from impaired Paneth cell antimicrobial function, such structural alteration of the microbiota does not trigger ileitis but, rather, aggravates dextran sodium sulfate-induced colitis. Hence, we conclude that defective autophagy in IECs may predispose to CD ileitis via impaired clearance of IRE1α aggregates during ER stress at this site.

Myeloid ATG16L1 Facilitates Host-Bacteria Interactions in Maintaining Intestinal Homeostasis

Intact ATG16L1 plays an essential role in Paneth cell function and intestinal homeostasis. However, the functional consequences of ATG16L1 deficiency in myeloid cells, particularly macrophages, are not fully characterized. We generated mice with Atg16l1 deficiency in myeloid and dendritic cells and showed that mice with myeloid Atg16l1 deficiency had exacerbated colitis in two acute and one chronic model of colitis with increased proinflammatory to anti-inflammatory macrophage ratios, production of proinflammatory cytokines, and numbers of IgA-coated intestinal microbes. Mechanistic analyses using primary murine macrophages showed that Atg16l1 deficiency led to increased reactive oxygen species production, impaired mitophagy, reduced microbial killing, impaired processing of MHC class II Ags, and altered intracellular trafficking to the lysosomal compartments. Increased production of reactive oxygen species and reduced microbial killing may be general features of the myeloid compartment, as they were also observed in Atg16l1-deficient primary murine neutrophils. A missense polymorphism (Thr³⁰⁰Ala) in the essential autophagy gene ATG16L1 is associated with Crohn disease (CD). Previous studies showed that this polymorphism leads to enhanced cleavage of ATG16L1 T300A protein and thus reduced autophagy. Similar findings were shown in primary human macrophages from controls and a population of CD patients carrying the Atg16l1 T300A risk variant and who were controlled for NOD2 CD-associated variants. This study revealed that ATG16L1 deficiency led to alterations in macrophage function that contribute to the severity of CD.

TIR-Domain-Containing Adapter-Inducing Interferon-β (TRIF) Regulates CXCR5+ T helper Cells in the Intestine

OBJECTIVE

Establishing an effective humoral immunity is an important host defense mechanism in intestinal mucosa. T follicular helper (Tfh) cells are a spectrum of CXCR5 expressing T helper cells that induce antigen-specific B cell differentiation. Because the differentiation of T helper cells is largely regulated by innate immunity, we addressed whether TRIF signaling regulates Tfh cell differentiation and its ability to trigger humoral immune responses in the intestine.

METHOD

CD4⁺CXCR5⁺ T cells, B cells, and plasma cells in the Peyer's patches (PPs) of WT and TRIF-deficient (Trif^LPS2) mice were analyzed by flow cytometry at the baseline, 9 days post primary infection, and 7 days post-secondary infection with Y. enterocolitica. Y. enterocolitica-specific CD4⁺CXCR5⁺ T cells were generated in vitro by co-culturing peritoneal macrophages with splenic naïve T cells in the presence of Y. enterocolitica lysate. WT and Trif^LPS2 mice received CD4⁺CXCR5⁺ T cells isolated either from Y. enterocolitica-primed WT mice or generated in vitro. These mice were infected with Y. enterocolitica and followed up to 4 weeks. Y. enterocolitica-specific IgA and IgG were measured in stool and serum samples, respectively.

RESULTS

At baseline, CD4⁺CXCR5⁺ T cell proportion was higher but the proportion of B cells and plasma cells was lower in the PPs of Trif^LPS2 mice compared to WT mice. After infection, the proportion of plasma cells also became higher in the PPs of Trif^LPS2 mice compared to WT mice. Corresponding increase of Y. enterocolitica-specific stool IgA but not serum IgG was found in Trif^LPS2 mice compared to WT mice. Both in vivo isolated and in vitro generated CD4⁺CXCR5⁺ T cells induced protective immunity against Y. enterocolitica infection.

CONCLUSION

Our results reveal a novel role of TRIF in the regulation of humoral immunity in the intestine that can be utilized as a basis for a unique vaccine strategy.

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

The frequency of fibrosing Crohn's disease (CD) is significant, with approximately 40% of CD patients with ileal disease developing clinically apparent strictures throughout their lifetime. Although strictures may be subdivided into fibrotic, inflammatory, or mixed forms, despite immunosuppressive therapy in CD patients in the form of steroids or immunomodulators, the frequency of fibrostenosing complications has still remained significant. A vast number of genetic and epigenetic variables are thought to contribute to fibrostenosing disease, including those that affect cytokine biology, and therefore highlight the complexity of disease, but also shed light on targetable pathways. Exclusively targeting fibrosis may be difficult, however, because of the relatively slow evolution of fibrosis in CD, and the potential adverse effects of inhibiting pathways involved in tissue repair and mucosal healing. Acknowledging these caveats, cytokine-targeted therapy has become the mainstay of treatment for many inflammatory conditions and is being evaluated for fibrotic disorders. The question of whether anti-cytokine therapy will prove useful for intestinal fibrosis is, therefore, acutely relevant. This review will highlight some of the current therapeutics targeting cytokines involved in fibrosis.

Systemic Activation of TLR3-Dependent TRIF Signaling Confers Host Defense against Gram-Negative Bacteria in the Intestine

Recognition of Gram-negative bacteria by toll-like receptor (TLR)4 induces MyD88 and TRIF mediated responses. We have shown that TRIF-dependent responses play an important role in intestinal defense against Gram-negative enteropathogens. In the current study, we examined underlying mechanisms of how systemic TRIF activation enhances intestinal immune defense against Gram-negative bacteria. First we confirmed that the protective effect of poly I:C against enteric infection of mice with Yersinia enterocolitica was dependent on TLR3-mediated TRIF signaling by using TLR3-deficient mice. This protection was unique in TRIF-dependent TLR signaling because systemic stimulation of mice with agonists for TLR2 (Pam3CSK4) or TLR5 (flagellin) did not reduce mortality on Y. enterocolitica infection. Systemic administration of poly I:C mobilized CD11c+, F4/80+, and Gr−1^hi cells from lamina propria and activated NK cells in the mesenteric lymph nodes (MLN) within 24 h. This innate immune cell rearrangement was type I IFN dependent and mediated through upregulation of TLR4 followed by CCR7 expression in these innate immune cells found in the intestinal mucosa. Poly I:C induced IFN-γ expression by NK cells in the MLN, which was mediated through type I IFNs and IL-12p40 from antigen presenting cells and consequent activation of STAT1 and STAT4 in NK cells. This formation of innate immunity significantly contributed to the elimination of bacteria in the MLN. Our results demonstrated an innate immune network in the intestine that can be established by systemic stimulation of TRIF, which provides a strong host defense against Gram-negative pathogens. The mechanism underlying TRIF-mediated protective immunity may be useful to develop novel therapies for enteric bacterial infection.

Ocular Manifestations in Inflammatory Bowel Disease Are Associated with Other Extra-intestinal Manifestations, Gender, and Genes Implicated in Other Immune-related Traits

BACKGROUND

There has been considerable progress in identifying inflammatory bowel disease [IBD] susceptibility genes but little progress in examining the role of genetic variation in the development of the extra-intestinal manifestations [EIMs] of IBD. This study identified clinical, serological, and genetic factors associated with ocular EIMs [O-EIMs] in IBD.

METHODS

We performed a retrospective case-control study of IBD patients, comparing those with and without O-EIMs using the Cedars-Sinai IBD Research Repository and the NIDDK IBD Genetics Consortium Repository. Genotyping was performed using Illumina whole genome platforms.

RESULTS

In all, 124 cases and 3328 controls with available clinical data were identified; 103 cases and 2808 controls had genetic data available. Erythema nodosum and peripheral arthritis particularly were common in patients with O-EIMs [p = 2.77 x 10(-13) and p = 2.58 x 10(-13), respectively] with increasing odds ratios for O-EIMs with each additional non-ocular-EIM [for ≥ 2 EIMs, odds ratio 14.72]. Nominal association with O-EIMs was observed at several known IBD susceptibility single nuclear polymorphisms. One locus, containing RBM19, achieved genome-wide level of significance for association with O-EIMs.

CONCLUSIONS

In IBD, O-EIMs co-occur with musculoskeletal and skin manifestations and, in this study, are nominally associated with known IBD loci. Additional cohorts are needed to verify these results and identify additional genes.

1,25-dihydroxyvitamin D3 regulates the development of chronic colitis by modulating both T helper (Th)1 and Th17 activation

T helper (Th)1 and Th17 cells play a critical role in inflammatory bowel disease (IBD). 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3 ) has emerged as a direct regulator of immune system function. Mice were grouped as follows: Control group (received PBS, n = 10), DSS group (received 2% DSS and PBS, n = 10), and DSS+VD group (received 2% DSS and 1,25(OH)2 D3 , n = 10). The disease activity index (DAI), colon length, and damage store of the mice were observed; the spleen length, weight, spleen index, and mononuclear cells of spleen were measured; mononuclear cells from mesenteric lymph nodes (MLN) were measured, and the levels of Th 1 and Th17 cytokines in the colon mucosa and spleen were measured. Mice in the DSS group developed severe diarrhea, rectal bleeding, and marked BW loss. Histological examination revealed extensive ulceration and inflammatory cell infiltration in the colon, and the structure of the spleen was disordered, infiltrated with inflammatory cytokines in red pulp. In the DSS group, mononuclear cell numbers from MLN and spleen were increased, and enhanced proteins and mRNA levels of Th 1 and Th17 cytokines were detected. In the DSS+VD group, 1,25(OH)2 D3 ameliorated the inflammation of the colon and spleen. In addition, 1,25(OH)2 D3 down-regulated the levels of Th 1 and Th17 cytokines. 1,25(OH)2 D3 represents a novel therapeutic drug for UC, which may correlate to inhibit the activation of Th1 and Th17 cells.

Effects of obesity on severity of colitis and cytokine expression in mouse mesenteric fat. Potential role of adiponectin receptor 1

In inflammatory bowel disease (IBD), obesity is associated with worsening of the course of disease. Here, we examined the role of obesity in the development of colitis and studied mesenteric fat-epithelial cell interactions in patients with IBD. We combined the diet-induce obesity with the trinitrobenzene sulfonic acid (TNBS) colitis mouse model to create groups with obesity, colitis, and their combination. Changes in the mesenteric fat and intestine were assessed by histology, myeloperoxidase assay, and cytokine mRNA expression by real-time PCR. Medium from human mesenteric fat and cultured preadipocytes was obtained from obese patients and those with IBD. Histological analysis showed inflammatory cell infiltrate and increased histological damage in the intestine and mesenteric fat of obese mice with colitis compared with all other groups. Obesity also increased the expression of proinflammatory cytokines including IL-1β, TNF-α, monocyte chemoattractant protein 1, and keratinocyte-derived chemokine, while it decreased the TNBS-induced increases in IL-2 and IFN-γ in mesenteric adipose and intestinal tissues. Human mesenteric fat isolated from obese patients and those with and IBD demonstrated differential release of adipokines and growth factors compared with controls. Fat-conditioned media reduced adiponectin receptor 1 (AdipoR1) expression in human NCM460 colonic epithelial cells. AdipoR1 intracolonic silencing in mice exacerbated TNBS-induced colitis. In conclusion, obesity worsens the outcome of experimental colitis, and obesity- and IBD-associated changes in adipose tissue promote differential mediator release in mesenteric fat that modulates colonocyte responses and may affect the course of colitis. Our results also suggest an important role for AdipoR1 for the fat-intestinal axis in the regulation of inflammation during colitis.

Anti-fibrogenic effects of the anti-microbial peptide cathelicidin in murine colitis-associated fibrosis

BACKGROUND AND AIMS

Cathelicidin (LL-37 in human and mCRAMP in mice) represents a family of endogenous antimicrobial peptides with anti-inflammatory effects. LL-37 also suppresses collagen synthesis, an important fibrotic response, in dermal fibroblasts. Here we determined whether exogenous cathelicidin administration modulates intestinal fibrosis in two animal models of intestinal inflammation and in human colonic fibroblasts.

METHODS

C57BL/6J mice (n=6 per group) were administered intracolonically with a trinitrobenzene sulphonic acid (TNBS) enema to induce chronic (6-7 weeks) colitis with fibrosis. mCRAMP peptide (5 mg/kg every 3 day, week 5-7) or cathelicidin gene (Camp)-expressing lentivirus (10⁷ infectious units week 4) were administered intracolonically or intravenously, respectively. 129Sv/J mice were infected with Salmonella typhimurium orally to induce cecal inflammation with fibrosis. Camp expressing lentivirus (10⁷ infectious units day 11) was administered intravenously.

RESULTS

TNBS-induced chronic colitis was associated with increased colonic collagen (col1a2) mRNA expression. Intracolonic cathelicidin (mCRAMP peptide) administration or intravenous delivery of lentivirus-overexpressing cathelicidin gene significantly reduced colonic col1a2 mRNA expression in TNBS-exposed mice, compared to vehicle administration. Salmonella infection also caused increased cecal inflammation associated with collagen (col1a2) mRNA expression that was prevented by intravenous delivery of Camp-expressing lentivirus. Exposure of human primary intestinal fibroblasts and human colonic CCD-18Co fibroblasts to transforming growth factor-beta1 (TGF-beta1) and/or insulin-like growth factor 1 induced collagen protein and mRNA expression, that was reduced by LL-37 (3-5 µM) through a MAP kinase-dependent mechanism.

CONCLUSION

Cathelicidin can reverse intestinal fibrosis by directly inhibiting collagen synthesis in colonic fibroblasts.

Inhibition of a novel fibrogenic factor Tl1a reverses established colonic fibrosis

Intestinal fibrostenosis is among the hallmarks of severe Crohn's disease. Patients with certain TNFSF15 (gene name for TL1A) variants over-express TL1A and have a higher risk of developing strictures in the small intestine. In addition, sustained Tl1a expression in mice leads to small and large intestinal fibrostenosis under colitogenic conditions. The aim of this study was to determine whether established murine colonic fibrosis could be reversed with Tl1a antibody (Ab). Treatment with neutralizing Tl1a Ab reversed colonic fibrosis back to the original pre-inflamed levels, potentially as a result of lowered expression of connective tissue growth factor, Il31Ra, transforming growth factor β1 and insulin-like growth factor-1. In addition, blocking Tl1a function by either neutralizing Tl1a Ab or deletion of death domain receptor 3 (Dr3) reduced the number of fibroblasts and myofibroblasts, the primary cell types that mediate tissue fibrosis. Primary intestinal myofibroblasts expressed Dr3 and functionally responded to direct Tl1a signaling by increasing collagen and Il31Ra expression. These data demonstrated a direct role for TL1A-DR3 signaling in tissue fibrosis and that modulation of TL1A-DR3 signaling could inhibit gut fibrosis.

Immunopathology of inflammatory bowel disease

Inflammatory bowel disease (IBD) results from a complex series of interactions between susceptibility genes, the environment, and the immune system. The host microbiome, as well as viruses and fungi, play important roles in the development of IBD either by causing inflammation directly or indirectly through an altered immune system. New technologies have allowed researchers to be able to quantify the various components of the microbiome, which will allow for future developments in the etiology of IBD. Various components of the mucosal immune system are implicated in the pathogenesis of IBD and include intestinal epithelial cells, innate lymphoid cells, cells of the innate (macrophages/monocytes, neutrophils, and dendritic cells) and adaptive (T-cells and B-cells) immune system, and their secreted mediators (cytokines and chemokines). Either a mucosal susceptibility or defect in sampling of gut luminal antigen, possibly through the process of autophagy, leads to activation of innate immune response that may be mediated by enhanced toll-like receptor activity. The antigen presenting cells then mediate the differentiation of naïve T-cells into effector T helper (Th) cells, including Th1, Th2, and Th17, which alter gut homeostasis and lead to IBD. In this review, the effects of these components in the immunopathogenesis of IBD will be discussed.

Mechanisms underlying effects of 1,25-Dihydroxyvitamin D3 on the Th17 cells

Th17 cells, a class of CD4(+) T cells, have been identified as novel effector cells, which play a pivotal role in several inflammatory and autoimmune diseases. 1,25-Dihydroxyvitamin D3 (1,25(OH)2D3), the active form of vitamin D, has emerged as a direct regulator of immune system function in humans. Accumulating reports demonstrated that 1,25(OH)2D3 possessed anti-inflammatory activity on Th17 cells to maintain immunologic homeostasis. This report will review the novel immune regulatory role of 1,25(OH)2D3 in its potential use for Th17 cell-related inflammatory and autoimmune conditions.

The antimicrobial peptide cathelicidin modulates Clostridium difficile-associated colitis and toxin A-mediated enteritis in mice

BACKGROUND

Clostridium difficile mediates intestinal inflammation by releasing toxin A (TxA), a potent enterotoxin. Cathelicidins (Camp as gene name, LL-37 peptide in humans and mCRAMP peptide in mice) are antibacterial peptides that also posses anti-inflammatory properties.

OBJECTIVES

To determine the role of cathelicidins in models of Clostridium difficile infection and TxA-mediated ileal inflammation and cultured human primary monocytes.

DESIGN

Wild-type (WT) and mCRAMP-deficient (Camp(-/-)) mice were treated with an antibiotic mixture and infected orally with C difficile. Some mice were intracolonically given mCRAMP daily for 3 days. Ileal loops were also prepared in WT mice and treated with either saline or TxA and incubated for 4 h, while some TxA-treated loops were injected with mCRAMP.

RESULTS

Intracolonic mCRAMP administration to C difficile-infected WT mice showed significantly reduced colonic histology damage, apoptosis, tissue myeloperoxidase (MPO) and tumour necrosis factor (TNF)α levels. Ileal mCRAMP treatment also significantly reduced histology damage, tissue apoptosis, MPO and TNFα levels in TxA-exposed ileal loops. WT and Camp(-/-) mice exhibited similar intestinal responses in both models, implying that C difficile/TxA-induced endogenous cathelicidin may be insufficient to modulate C difficile/TxA-mediated intestinal inflammation. Both LL-37 and mCRAMP also significantly reduced TxA-induced TNFα secretion via inhibition of NF-κB phosphorylation. Endogenous cathelicidin failed to control C difficile and/or toxin A-mediated inflammation and even intestinal cathelicidin expression was increased in humans and mice.

CONCLUSION

Exogenous cathelicidin modulates C difficile colitis by inhibiting TxA-associated intestinal inflammation. Cathelicidin administration may be a new anti-inflammatory treatment for C difficile toxin-associated disease.

SUSTAINED TL1A (TNFSF15) EXPRESSION ON BOTH LYMPHOID AND MYELOID CELLS LEADS TO MILD SPONTANEOUS INTESTINAL INFLAMMATION AND FIBROSIS

TL1A is a member of the TNF superfamily, and its expression is increased in the mucosa of inflammatory bowel disease patients. Moreover, patients with certain TNFSF15 variants over-express TL1A and have a higher risk of developing strictures in the small intestine. Consistently, mice with sustained Tl1a expression in either lymphoid or myeloid cells develop spontaneous ileitis and increased intestinal collagen deposition. Transgenic (Tg) mice with constitutive Tl1a expression in both lymphoid and myeloid cells were generated to assess their in vivo consequence. Constitutive expression of Tl1a in both lymphoid and myeloid cells showed increased spontaneous ileitis and collagen deposition than WT mice. T cells with constitutive expression of Tl1a in both lymphoid and myeloid cells were found to have a more activated phenotype, increased gut homing marker CCR9 expression, and enhanced Th1 and Th17 cytokine activity than WT mice. Although no differences in T cell activation marker, Th1 or Th17 cytokine activity, ileitis, or collagen deposition were found between constitutive Tl1a expression in lymphoid only, myeloid only, or combined lymphoid and myeloid cells. Double hemizygous Tl1a-Tg mice appeared to have worsened ileitis and intestinal fibrosis. Our findings confirm that TL1A-DR3 interaction is involved in T cell-dependent ileitis and fibrosis.

Differential expression of PTEN in hepatic tissue and hepatic stellate cells during rat liver fibrosis and its reversal

To evaluate the change in phosphatase and tensin homology deleted on chromosome ten (PTEN) expression in liver fibrogenesis, particularly the reversal of fibrogenic liver tissues, and to investigate the relation with the proliferation and apoptosis of hepatic stellate cells (HSCs) in vivo, a rat model of hepatic fibrosis was established by hypodermic injection of carbon tetrachloride (CCl4) mixed with olive oil at the concentration of 40% for 5 weeks (2 ml/kg, twice a week). Reversal of fibrosis was achieved with normal feedings for 4 weeks after CCl4 injection for 5 weeks. The expression of PTEN was measured by immunofluorescence, western blot analysis and real-time PCR. Co-expression of α-smooth muscle actin (α-SMA) with PTEN and α-SMA with terminal deoxynucleotidyltransferase-mediated dUTP nick end labelling (TUNEL) were assessed by confocal laser scanning microscopy. The results displayed that the expression of PTEN was reduced with fibrosis in both rat liver tissues and activated HSCs. By contrast, PTEN expression was increased with the reversal of liver fibrosis. Compared to the fibrogenic state, there were increased numbers of apoptotic activated HSCs during reversal of fibrosis. These data suggest that the dynamic expression of PTEN in rat liver tissues is negatively correlated with liver fibrosis and activated HSCs and is positively correlated with reversal of fibrosis and apoptotic activated HSCs. Modulation of PTEN expression may be an effective and novel method for the treatment of liver fibrosis.

Split-dose administration of thiopurine drugs: a novel and effective strategy for managing preferential 6-MMP metabolism

BACKGROUND

Mercaptopurine and azathioprine (AZA) are efficacious in treating IBD. 6-tioguanine (6-TGN) levels correlate with therapeutic efficacy, whereas high 6-methylmercaptopurine (6-MMP) levels are associated with hepatotoxicity and myelotoxicity. Some IBD patients exhibit dose-limiting preferential 6-MMP production, which may lead to undesired side effects and impact efficacy.

AIM

To review the outcomes of thiopurine split-dosing in patients with preferential 6-MMP metabolism.

METHODS

A retrospective chart review of 179 IBD patients treated at the Cedars-Sinai IBD Center with AZA or mercaptopurine was performed. Preferential 6-MMP metabolisers with 6-MMP levels greater than 7000 pmol/8 × 10(8) erythrocytes who underwent split-dosing were identified and assessed for biochemical and clinical responses to these dose modifications.

RESULTS

A total of 20 of 179 patients met the criteria for preferential 6-MMP metabolism and underwent thiopurine split-dosing. Dividing the total daily thiopurine dose led to a reduction in 6-MMP levels (11785 vs. 5324 pmol/8 × 10(8) erythrocytes; P < 0.0001) without negatively affecting clinical disease activity or 6-TGN levels (239 vs. 216 pmol/8 × 10(8) erythrocytes; P = N.S.) and led to resolution of 6-MMP associated side effects (elevated transaminases, leucopenia and flu-like symptoms) in all but two patients. After mean follow-up of 36 months, 12 patients remained in clinical remission on split-dose mercaptopurine. Five of the remaining eight patients escalated to anti-TNF therapy, two progressed to surgery, and one switched to tioguanine therapy.

CONCLUSION

Split-dose administration of mercaptopurine/AZA represents an alternative option in IBD patients with preferential 6-MMP metabolism who might otherwise require steroid exposure or escalation of therapy.

Protective role of 1,25(OH)2 vitamin D3 in the mucosal injury and epithelial barrier disruption in DSS-induced acute colitis in mice

Background

Intestinal hyper-permeability plays a critical role in the etiopathogenesis of inflammatory bowel disease (IBD) by affecting the penetration of pathogens, toxic compounds and macromolecules. 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], the active form of vitamin D, has been shown to be an important regulator of IBD and recent epidemiology suggests that patients with IBD have an impaired vitamin D status. The purpose of this study is to investigate the possible protective effects of 1,25(OH)₂D₃ on mucosal injury and epithelial barrier disruption on dextran sulfate sodium (DSS)-induced acute colitis model.

Methods

We used DSS-induced acute colitis model to investigate the protective effects of 1,25(OH)₂D₃ on mucosal injury and epithelial barrier integrity. Severity of colitis was evaluated by disease activity index (DAI), body weight (BW) change, colon length, histology, myeloperoxidase (MPO) activity, and proinflammatory cytokine production including tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). In vitro the protective role of 1,25(OH)₂D₃ was assessed by incubating Caco-2 cells with or without DSS and measuring transepithelial electrical resistance (TEER) and fluorescein isothiocyanate dextran (FITC-D). The intestinal permeability was analyzed by FITC-D, bacterial translocation and measurement of lipopolysaccharide (LPS). Ultrastructural features of the colon tissue and Caco-2 cell monolayer were observed by electron microscopy. Expressions of tight junction (TJ) proteins in the colon mucosa and Caco-2 cells were detected by immunohistochemistry, immunofluorescence, Western blot and real-time fluorescent quantitative PCR, respectively.

Results

DSS-induced acute colitis model was characterized by a reduced BW, AUC of BW, serum calcium, higher DAI, AUC of DAI, shortened colon length, elevated MPO activity, worsened histologic inflammation, increased mononuclear cell numbers in mesenteric lymph nodes (MLNs) and colonic lamina propria (LP), and enhanced proteins and mRNA levels of TNF-α and IFN-γ. 1,25(OH)₂D₃ markedly increased expressions of TJ proteins and mRNA and decreased the FITC-D permeability and the level of LPS. Furthermore, 1,25(OH)₂D₃ abrogated bacterial translocation to MLNs and ameliorated ultrastructural features of the colon epithelium by scanning electron microscopy (SEM). In vitro, 1,25(OH)₂D₃ increased TEER, TJ proteins and mRNA expressions, decreased the FITC-D permeability, and preserved structural integrity of the TJ in Caco-2 cells.

Conclusions

1,25(OH)₂D₃ may play a protective role in mucosal barrier homeostasis by maintaining the integrity of junction complexes and in healing capacity of the colon epithelium. 1,25(OH)₂D₃ may represent an attractive and novel therapeutic agent for the adjuvant therapy of IBD.

Inflammatory Bowel Disease Associated Colorectal Neoplasia

Patients with ulcerative colitis (UC) or Crohn’s colitis have a greater risk for developing colorectal cancer (CRC). Many studies have described the evolving epidemiology and risk factors for CRC in patients with inflammatory bowel disease (IBD). Recent evidence indicates that the incidence has been decreasing with the advancement of medical and surgical therapies, and surveillance has emerged as the foundation of prevention. Chemoprophylaxis is another area of research; however, given the limited efficacy of these agents, they are only being used in conjunction with endoscopic surveillance. Our ability to formulate effective strategies for the prevention of this dreaded complication expands as more is discovered of the molecular events underlying IBD carcinogenesis. Management strategies are constantly updated as new evidence and endoscopic techniques emerge. In this paper, we review the literature regarding epidemiology, pathogenesis, risk factors and chemoprophylaxis as well as the latest consensus guidelines for management of dysplasia and neoplasia in IBD patients.

Optimizing 6-mercaptopurine and azathioprine therapy in the management of inflammatory bowel disease

The thiopurine drugs, 6-mercaptopurine (6-MP) and azathioprine, are efficacious in the arsenal of inflammatory bowel disease (IBD) therapy. Previous reports indicate that 6-thioguanine nucleotide (6-TGN) levels correlate with therapeutic efficacy, whereas high 6-methylmercaptopurine (6-MMP) levels are associated with hepatotoxicity and myelotoxicity. Due to their complex metabolism, there is wide individual variation in patient response therein, both in achieving therapeutic drug levels as well as in developing adverse reactions. Several strategies to optimize 6-TGN while minimizing 6-MMP levels have been adopted to administer the thiopurine class of drugs to patients who otherwise would not tolerate these drugs due to side-effects. In this report, we will review different approaches to administer the thiopurine medications, including the administration of 6-mercaptopurine in those unsuccessfully treated with azathioprine; co-administration of thiopurine with allopurinol; co-administration of thiopurine with anti-tumor necrosis factor α; 6-TGN administration; desensitization trials; and split dosing of 6-MP.

Substance P induces CCN1 expression via histone deacetylase activity in human colonic epithelial cells

We have shown that substance P (SP) and its neurokinin-1 receptor (NK-1R) regulate intestinal angiogenesis by increasing expression of protein CYR61 (the cysteine-rich angiogenic inducer 61, or CCN1) in colonic epithelial cells. However, the mechanism involved in SP-induced CCN1 expression has not been studied, and the outcome of increased CCN1 expression in the development of colitis is not fully understood. Because histone deacetylase (HDAC) modulates transcription of several genes involved in inflammation, we investigated participation of HDAC in SP-induced CCN1 expression in human colonic epithelial NCM460 cells overexpressing NK-1R (NCM460-NK-1R) and in primary colonocytes. SP increased HDAC activity with deacetylation and dephosphorylation of nucleosome protein histone H3 in NCM460-NK-1R and/or primary colonocytes. Histone deacetylation and dephosphorylation was observed in colonic mucosa from irritable bowel disease patients. Similarly, colonic mucosal tissues from mice exposed to dextran sulfate sodium showed histone H3 deacetylation and dephosphorylation and increased HDAC activity that was reversed by the NK-1R antagonist CJ-12255. SP-induced increased CCN1 expression in NCM460-NK-1R cells was abolished by pharmacological HDAC inhibition. HDAC overexpression activated basal and SP-induced CCN1 promoter activity. Intracolonic CCN1 overexpression significantly ameliorated dextran sulfate sodium-induced colitis, with reduction of proinflammatory cytokine expression in mice. Thus, SP-mediated CCN1 expression in the inflamed human and mouse colon involves increased HDAC activity. Our results strongly suggest that increased CCN1 expression may be involved in mucosal healing during colitis.

Variants in ZNF365 isoform D are associated with Crohn's disease

OBJECTIVE

Genome-wide association studies have identified multiple Crohn's disease (CD) susceptibility loci, including association with non-coding intergenic single-nucleotide polymorphisms (SNPs) at 10q21.

DESIGN

To fine-map the 10q21 locus, the authors genotyped 86 SNPs in 1632 CD cases and 961 controls and performed single-marker and conditional analyses using logistic regression.

RESULTS

Association with CD risk spanning 11 SNPs (p<0.001) was observed. The most significant association observed was at the non-synonymous SNP, rs7076156 (Ala62Thr), in ZNF365. The alanine allele was over-represented in CD (p=5.23×10⁻⁷; OR=1.39 (95% CI 1.22 to 1.58)); allele frequency of 76% in CD and 69.7% in controls). Conditional analysis on rs7076156 nullified all other significant associations, suggesting that this is the causative variant at this locus. Four isoforms of ZNF365 have previously been identified, and rs7076156 is located in an exon unique to ZNF365 isoform D. The authors demonstrated, using reverse transcription-PCR, expression of ZNF365D in intestinal resections from both CD subjects and controls. Markedly reduced mean expression levels of ZNF365D were identified in Epstein-Barr virus-transformed lymphoblastoid cell lines from CD subjects homozygous for the risk allele (Ala). A whole-genome microarray expression study further suggested that the Ala62Thr change in ZNF365 isoform D is related to differential expression of the genes ARL4A, MKKS, RRAGD, SUMF2, TDR1 and ZNF148 in CD.

CONCLUSIONS

Collectively, these data support the hypothesis that the non-synonymous Ala62Thr SNP, rs7076156, underlies the association between 10q21 and CD risk and suggest that this SNP acts by altering expression of genes under the control of ZNF365 isoform D.

A case of steroid-dependent myeloid granulocytic sarcoma masquerading as Crohn’s disease

Small bowel tumors and Crohn’s disease are common causes of small bowel obstruction. Early stage neoplasms can easily be mistaken for Crohn’s disease. Therefore, thorough work-ups including imaging studies and endoscopic evaluation with biopsies are critical for accurate diagnosis. Here we report a case of an otherwise healthy female with progressive onset of multiple, recurrent obstructive symptoms secondary to terminal ileal narrowing who was referred for management of steroid-dependent Crohn’s disease. After thorough evaluation, the diagnosis was revised to myeloid granulocytic sarcoma involving the terminal ileum. In this case, a delay in diagnosis can be detrimental for prognosis, as myeloid granulocytic sarcoma is highly predictive of underlying acute myeloid leukemia and needs urgent referral for chemotherapy and/or resection.

CD161 DEFINES EFFECTOR T CELLS THAT EXPRESS LIGHT AND RESPOND TO TL1A-DR3 SIGNALING

Expression of NK cell markers identifies pro-inflammatory T cell subsets in the liver and intestinal immune compartments. Specifically, CD161 is expressed on Th17 cells which play an important role in the regulation of mucosal inflammation. In this study, we characterized human peripheral blood CD161+ T cells as an effector population partially resembling a gut T cell phenotype. CD161+ CD4+ T cells express the gut-associated TNF family member, LIGHT, and respond to crosslinking of DR3, a receptor to another gut-associated cytokine, TL1A. Robust IFN-γ production in response to DR3 signaling correlated with enhanced expression of surface DR3 on CD161+ T cells and co-stimulation with IL12 and IL18. CD161+ T cell effector function was directly demonstrated by activation of responder monocytes in co-culture leading to CD40 upregulation and CD14 downregulation. CD161+ T cells reciprocally responded to activated monocytes, inducing expression of activation marker, CD69, and production of IL2 and IFN-γ, further demonstrating effective CD161+ T cell cross-talk with monocytes. Finally, CD161 defined a subset of T cells that co-express CD56, a second NK marker. Our findings implicate human CD161+ T cells in gut-associated signaling mechanisms, and suggest a monocyte mediated effector function in mucosal inflammation.

Down-regulation of focal adhesion kinase by short hairpin RNA increased apoptosis of rat hepatic stellate cells

Focal adhesion kinase (FAK) plays an essential role in the activation of hepatic stellate cells (HSC). The role of FAK on proliferation and apoptosis of fibronectin (FN)-stimulated HSC was investigated using short hairpin RNA (shRNA)-mediated gene silencing technology. FAK shRNA decreased the expressions of FAK, p-FAK (Tyr(397)), ERK(1), and p-ERK(1). FAK gene silencing also inhibited HSC proliferation by 11.08% at 12-h, 15.12% at 24-h, and 28.62% at 48-h post-transfection. Flow cytometric analysis (FACS) revealed that the apoptotic rate at 24 h was increased in the FAK shRNA plasmid group compared with the HK group (8.29 ± 0.79% vs 2.70 ± 0.31%, p < 0.01). TUNEL also confirmed the increase in the rate of apoptosis (19.00 ± 0.92% vs 7.63 ± 0.70%, p < 0.01), and studies showed that the caspase-3 expression was increased while the ratio of Bcl-2 to Bax was decreased. Together, these data show that FAK regulates HSC proliferation and induces the apoptosis of HSC via the caspase-3 and Bcl-2/Bax pathway.

Fucosyltransferase 2 (FUT2) non-secretor status is associated with Crohn's disease

Genetic variation in both innate and adaptive immune systems is associated with Crohn's disease (CD) susceptibility, but much of the heritability to CD remains unknown. We performed a genome-wide association study (GWAS) in 896 CD cases and 3204 healthy controls all of Caucasian origin as defined by multidimensional scaling. We found supportive evidence for 21 out of 40 CD loci identified in a recent CD GWAS meta-analysis, including two loci which had only nominally achieved replication (rs4807569, 19p13; rs991804, CCL2/CCL7). In addition, we identified associations with genes involved in tight junctions/epithelial integrity (ASHL, ARPC1A), innate immunity (EXOC2), dendritic cell biology [CADM1 (IGSF4)], macrophage development (MMD2), TGF-beta signaling (MAP3K7IP1) and FUT2 (a physiological trait that regulates gastrointestinal mucosal expression of blood group A and B antigens) (rs602662, P=3.4x10(-5)). Twenty percent of Caucasians are 'non-secretors' who do not express ABO antigens in saliva as a result of the FUT2 W134X allele. We demonstrated replication in an independent cohort of 1174 CD cases and 357 controls between the four primary FUT2 single nucleotide polymorphisms (SNPs) and CD (rs602662, combined P-value 4.90x10(-8)) and also association with FUT2 W143X (P=2.6x10(-5)). Further evidence of the relevance of this locus to CD pathogenesis was demonstrated by the association of the original four SNPs and CD in the recently published CD GWAS meta-analysis (rs602662, P=0.001). These findings strongly implicate this locus in CD susceptibility and highlight the role of the mucus layer in the development of CD.

Microbial induction of inflammatory bowel disease associated gene TL1A (TNFSF15) in antigen presenting cells

TL1A is a member of the TNF superfamily and its expression is increased in the mucosa of inflammatory bowel disease patients. Neutralizing anti-mouse TL1A Ab attenuates chronic colitis in two T-cell driven murine models, suggesting that TL1A is a central modulator of gut mucosal inflammation in inflammatory bowel disease. We showed previously that TL1A is induced by immune complexes via the Fc gamma R signaling pathway. In this study, we report that multiple bacteria, including gram negative organisms (E. coli, E. coli Nissle 1917, Salmonella typhimurium), gram positive organisms (Listeria monocytogenes, Staphylococcus epidermidis), partial anaerobes (Campylobacter jejuni), and obligate anaerobes (Bacteroides thetaiotaomicron, Bifidobacterium breve, Clostridium A4) activate TL1A expression in human APC, including monocytes and monocyte-derived DC. Bacterially induced TL1A mRNA expression correlates with the detection of TL1A protein levels. TL1A induced by bacteria is mediated in part by the TLR signaling pathway and inhibited by downstream blockade of p38 MAPK and NF-kappaB activation. Microbial induction of TL1A production by human APC potentiated CD4(+) T-cell effector function by augmenting IFN-gamma production. Our findings suggest a role for TL1A in pro-inflammatory APC-T cell interactions and implicate TL1A in host responses to enteric microorganisms.

Recent advances in IBD pathogenesis: genetics and immunobiology

The inflammatory bowel diseases (IBDs), Crohn's disease and ulcerative colitis, are chronic inflammatory disorders caused by dysregulated immune responses in genetically predisposed individuals. Although the precise etiology of IBD remains unclear, accumulating data, including genome-wide association studies, have advanced our understanding of its immunopathogenesis. This review highlights the role in gut homeostasis and IBD pathogenesis of autophagy, the interleukin (IL)-23/IL-17 axis, and a novel member of the tumor necrosis factor family, TL1A. It focuses on advances in our understanding of IBD from the past year, including advances in genetics and immunobiology.

Immunopathogenesis of inflammatory bowel disease

Crohn’s disease and ulcerative colitis are chronic relapsing immune mediated disorders that results from an aberrant response to gut luminal antigen in genetically susceptible host. The adaptive immune response that is then triggered was widely considered to be a T-helper-1 mediated condition in Crohn’s disease and T-helper-2 mediated condition in ulcerative colitis. Recent studies in animal models, genome wide association, and basic science has provided important insights in in the immunopathogenesis of inflammatory bowel disease, one of which was the characterization of the interleukin-23/Th-17 axis.

All Roads Lead to Rome: Update on Rome III Criteria and New Treatment Options

The recently published Rome III criteria reflect current understanding of functional gastrointestinal disorders. These criteria include definitions of these conditions and their pathophysiologic subtypes and offer guidelines for their management. At the 2006 Annual Scientific Meeting of the American College of Gastroenterology, a panel of experts discussed these criteria as they pertain to irritable bowel syndrome, functional dyspepsia, and chronic constipation. This article reviews the panel's findings, highlights the differences between the Rome II and III criteria, and summarizes best treatment options currently available to practitioners and their patients.

Islet secretory defect in insulin receptor substrate 1 null mice is linked with reduced calcium signaling and expression of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)-2b and -3

Mice with deletion of insulin receptor substrate (IRS)-1 (IRS-1 knockout [KO] mice) show mild insulin resistance and defective glucose-stimulated insulin secretion and reduced insulin synthesis. To further define the role of IRS-1 in islet function, we examined the insulin secretory defect in the knockouts using freshly isolated islets and primary beta-cells. IRS-1 KO beta-cells exhibited a significantly shorter increase in intracellular free Ca(2+) concentration ([Ca(2+)](i)) than controls when briefly stimulated with glucose or glyceraldehyde and when l-arginine was used to potentiate the stimulatory effect of glucose. These changes were paralleled by a lower number of exocytotic events in the KO beta-cells in response to the same secretagogues, indicating reduced insulin secretion. Furthermore, the normal oscillations in intracellular Ca(2+) and O(2) consumption after glucose stimulation were dampened in freshly isolated KO islets. Semiquantitative RT-PCR showed a dramatically reduced islet expression of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)-2b and -3 in the mutants. These data provide evidence that IRS-1 modulation of insulin secretion is associated with Ca(2+) signaling and expression of SERCA-2b and -3 genes in pancreatic islets and provides a direct link between insulin resistance and defective insulin secretion.