Inhibition of Smad7 with a specific antisense oligonucleotide facilitates TGF-beta1-mediated suppression of colitis

Very early onset IBD: novel genetic aetiologies

PURPOSE OF REVIEW

To summarize the current understanding and recent advances on the genetic aetiology in the pathogenesis of very early onset inflammatory bowel disease (VEO-IBD).

RECENT FINDINGS

IBD is a chronic disorder of the gastrointestinal tract whose manifestation is a result of complex interactions between genetics, environment, immune system and microbial flora. Over 230 IBD risk loci have been reported in genome wide association studies but the genetic contribution of the majority of these loci in the manifestation of IBD is very low. Patients with VEO-IBD present with a more severe disease than older patients, characterized by poor prognosis and failure of conventional therapy. Recent studies have reported several monogenic diseases with high penetrance that present with IBD and IBD-like intestinal manifestations and overlap with primary immunodeficiencies. Increasing body of evidence supports a prominent role of genetics in the onset of VEO-IBD. New genetic variants and diagnoses in VEO-IBD are reviewed and current challenges in therapy with potential strategy to manage the disease are discussed.

SUMMARY

Functional analysis of the genes implicated in monogenic IBD has increased the understanding of the underlying pathobiological mechanism of the disease. This knowledge can be used to personalize medicine for specific patients, improving the standard of care and quality of life.

Oligonucleotide-Based Therapies for Inflammatory Bowel Disease

The growing understanding of the immunopathogenesis of inflammatory bowel diseases (IBDs) has contributed to the identification of new targets whose expression/activity can be modulated for therapeutic purposes. Several approaches have been employed to develop selective pharmaceutical compounds; among these, antisense oligonucleotides (ASOs) or synthetic oligonucleotides represent a valid option for inhibiting or enhancing, respectively, the expression/function of molecules that have been implicated in the control of IBD-related inflammation. In this context, data have been accumulated for the following compounds: alicaforsen, an ASO targeting intercellular adhesion molecule-1, a transmembrane glycoprotein that regulates rolling and adhesion of leukocytes to inflamed intestine; DIMS0150 and BL-7040, two oligonucleotides that enhance Toll-like receptor-9 activity; Mongersen, an ASO that inhibits Smad7, thereby restoring transforming growth factor-β1/Smad-associated signaling; STNM01, a double-stranded RNA oligonucleotide silencing carbohydrate sulfotransferase, an enzyme involved in fibrogenic processes, and hgd40, a specific DNAzyme inhibiting expression of the transcription factor GATA3. In this article, we review the rationale and the available data relative to the use of these agents in IBD. Although pre-clinical and phase II trials in IBD support the use of oligonucleotide-based therapies for treating the pathogenic process occurring in the gut of patients with these disorders, further work is needed to establish whether and which patients can benefit from specific ASOs and identify biomarkers that could help optimize treatment.

Cytomegalovirus promotes intestinal macrophage-mediated mucosal inflammation through induction of Smad7

Intestinal macrophages in healthy human mucosa are profoundly down-regulated for inflammatory responses (inflammation anergy) due to stromal TGF-β inactivation of NF-κB. Paradoxically, in cytomegalovirus (CMV) intestinal inflammatory disease, one of the most common manifestations of opportunistic CMV infection, intestinal macrophages mediate severe mucosal inflammation. Here we investigated the mechanism whereby CMV infection promotes macrophage-mediated mucosal inflammation. CMV infected primary intestinal macrophages but did not replicate in the cells or reverse established inflammation anergy. However, CMV infection of precursor blood monocytes, the source of human intestinal macrophages in adults, prevented stromal TGF-β-induced differentiation of monocytes into inflammation anergic macrophages. Mechanistically, CMV up-regulated monocyte expression of the TGF-β antagonist Smad7, blocking the ability of stromal TGF-β to inactivate NF-κB, thereby enabling MyD88 and NF-κB-dependent cytokine production. Smad7 expression also was markedly elevated in mucosal tissue from subjects with CMV colitis and declined after antiviral ganciclovir therapy. Confirming these findings, transfection of Smad7 antisense oligonucleotide into CMV-infected monocytes restored monocyte susceptibility to stromal TGF-β-induced inflammation anergy. Thus, CMV-infected monocytes that recruit to the mucosa, not resident macrophages, are the source of inflammatory macrophages in CMV mucosal disease and implicate Smad7 as a key regulator of, and potential therapeutic target for, CMV mucosal disease.

Advances in understanding the role of cytokines in inflammatory bowel disease

Cytokines represent the key pathophysiologic elements that govern the initiation, progression, and, in some circumstances, the resolution of the inflammation occurring in inflammatory bowel disease (IBD). Areas covered: In this review, we will focus on the main effector and anti-inflammatory cytokines produced in IBD and discuss the results of recent trials in which cytokine-based therapy has been used for treating IBD patients. Expert commentary: The possibility to sample mucosal biopsies from IBD patients and analyze which molecular pathways are prominent during the active phases of the disease and the easy access to various models of experimental colitis has largely advanced our understanding about the role of cytokines in IBD. These progresses have facilitated the development of several therapeutic compounds, which either target inflammatory cytokines or enhance the regulatory function of immunosuppressive cytokines. While some of such drugs are effective in the induction and maintenance of remission of the disease, other compounds are not useful for attenuating the ongoing mucosal inflammation, thus establishing a hierarchical scale of the relevance of cytokines in IBD. Further work is needed to identify biomarkers, which could help personalize cytokine-targeted therapy and minimize potential side effects.

Chemokines and Chemokine Receptors as Therapeutic Targets in Inflammatory Bowel Disease; Pitfalls and Promise

The principal targets for anti-chemokine therapy in inflammatory bowel disease (IBD) have been the receptors CCR9 and CXCR3 and their respective ligands CCL25 and CXCL10. More recently CCR6 and its ligand CCL20 have also received attention, the expression of the latter in enterocytes being manipulated through Smad7 signalling. These pathways, selected based on their fundamental role in regulating mucosal immunity, have led to the development of several therapeutic candidates that have been tested in early phase clinical trials with variable clinical efficacy. In this article, we appraise the status of chemokine-directed therapy in IBD, review recent developments, and nominate future areas for therapeutic focus.

Reciprocal Regulation Between Smad7 and Sirt1 in the Gut

In inflammatory bowel disease (IBD) mucosa, there is over-expression of Smad7, an intracellular inhibitor of the suppressive cytokine transforming growth factor-β1, due to post-transcriptional mechanisms that enhance Smad7 acetylation status thus preventing ubiquitination-mediated proteosomal degradation of the protein. IBD-related inflammation is also marked by defective expression of Sirt1, a class III NAD+-dependent deacetylase, which promotes ubiquitination-mediated proteosomal degradation of various intracellular proteins and triggers anti-inflammatory signals. The aim of our study was to determine whether, in IBD, there is a reciprocal regulation between Smad7 and Sirt1. Smad7 and Sirt1 were examined in mucosal samples of IBD patients and normal controls by Western blotting and immunohistochemistry, and Sirt1 activity was assessed by a fluorimetric assay. To determine whether Smad7 is regulated by Sirt1, normal or IBD lamina propria mononuclear cells (LPMC) were cultured with either Sirt1 inhibitor (Ex527) or activator (Cay10591), respectively. To determine whether Smad7 controls Sirt1 expression, ex vivo organ cultures of IBD mucosal explants were treated with Smad7 sense or antisense oligonucleotide. Moreover, Sirt1 expression was evaluated in LPMC isolated from Smad7-transgenic mice given dextran sulfate sodium (DSS). Upregulation of Smad7 was seen in both the epithelial and lamina propria compartments of IBD patients and this associated with reduced expression and activity of Sirt1. Activation of Sirt1 in IBD LPMC with Cay10591 reduced acetylation and enhanced ubiquitination-driven proteasomal-mediated degradation of Smad7, while inhibition of Sirt1 activation in normal LPMC with Ex527 increased Smad7 expression. Knockdown of Smad7 in IBD mucosal explants enhanced Sirt1 expression, thus suggesting a negative effect of Smad7 on Sirt1 induction. Consistently, mucosal T cells of Smad7-transgenic mice contained reduced levels of Sirt1, a defect that was amplified by induction of DSS colitis. The data suggest the existence of a reciprocal regulatory mechanism between Smad7 and Sirt1, which could contribute to amplify inflammatory signals in the gut.

Inflammatory bowel disease: new therapies from antisense oligonucleotides

Inflammatory bowel diseases (IBD) are chronic inflammatory conditions of the gastrointestinal tract encompassing two main clinical entities: Crohn's disease (CD) and ulcerative colitis (UC). These disorders are characterized by various grades of tissue damage and development of local complications and extra-intestinal manifestations. The cause of IBD remains unknown but accumulating evidence indicates that both CD and UC arise in genetically predisposed individuals as a result of the action of multiple environmental factors, which ultimately trigger excessive and poorly controlled immune response against antigens of the luminal flora. Despite this realization, a full understanding of IBD pathogenesis is still out of reach and, consequently, treatment is far from optimal. However, in recent years, several pathways of intestinal damage have been delineated and the improved knowledge has contributed to the development of new therapies. Various approaches have been used to either inhibit the expression and/or function of inflammatory molecules or enhance counter-regulatory mechanisms. This review summarizes the available pre-clinical and clinical data for antisense oligonucleotides and oligonucleotide-based therapy to provide a comprehensive understanding of the rationale and mechanism of action of these compounds in IBD. Key messages Preclinical studies and clinical trials show that antisense oligonucleotide (ASO)-based therapy could be of benefit in inflammatory bowel diseases. ASOs have an excellent safety profile. Technical issues emerged from clinical trials suggest that changes in drug formulation and/or route of administration could improve ASO efficacy.

Transforming Growth Factor-β1/Smad7 in Intestinal Immunity, Inflammation, and Cancer

In physiological conditions, the activity of the intestinal immune system is tightly regulated to prevent tissue-damaging reactions directed against components of the luminal flora. Various factors contribute to maintain immune homeostasis and diminished production and/or function of such molecules trigger and/or propagate detrimental signals, which can eventually lead to chronic colitis and colon cancer. One such a molecule is transforming growth factor-β1 (TGF-β1), a cytokine produced by many inflammatory and non-inflammatory cells and targeting virtually all the intestinal mucosal cell types, with the down-stream effect of activating intracellular Smad2/3 proteins and suppressing immune reactions. In patients with inflammatory bowel diseases (IBD), there is defective TGF-β1/Smad signaling due to high Smad7, an inhibitor of TGF-β1 activity. Indeed, knockdown of Smad7 with a specific antisense oligonucleotide restores endogenous TGF-β1 activity, thereby inhibiting inflammatory pathways in patients with IBD and colitic mice. Consistently, mice over-expressing Smad7 in T cells develop severe intestinal inflammation in various experimental models. Smad7 expression is also upregulated in colon cancer cells, in which such a protein controls positively intracellular pathways that sustain neoplastic cell growth and survival. We here review the role of TGF-β1 and Smad7 in intestinal immunity, inflammation, and cancer.

SMAD7 regulates proinflammatory and prolabor mediators in amnion and myometrium

Preterm birth continues to be a significant public health problem. Infection (bacterial and or viral) and inflammation, by stimulating proinflammatory cytokines, adhesion molecules, and matrix metalloproteinase 9 (MMP9), play a central role in the rupture of membranes and myometrial contractions. SMAD7 has been implicated in regulating the inflammatory response; however, no studies have been performed with regard to human labor. In this study, we determined the effect of spontaneous human labor and prolabor mediators on SMAD7 expression in myometrium and fetal membranes. Functional studies were employed to investigate the effect of siRNA knockdown of SMAD7 (siSMAD7) in regulating infection and inflammation-induced prolabor mediators. SMAD7 mRNA and protein expression were significantly higher with spontaneous term labor, compared to no labor, in myometrium and fetal membranes. SMAD7 expression was also significantly higher in amnion from women with preterm chorioamnionitis. The proinflammatory cytokines IL1B and TNF, the bacterial product fsl-1, and the viral dsRNA analog poly(I:C) significantly increased SMAD7 in myometrial cells and amnion cells. In myometrial cells, siSMAD7 cells significantly decreased cytokine (IL6) and chemokine (CXCL1, CXCL8, CCL2 are also known as GRO-alpha, interleukin (IL)-8 and monocyte chemotactic protein-1 (MCP-1)) production induced by IL1B, TNF, and fsl-1. There was also a decrease in the expression of adhesion molecules intercellular adhesion molecule 1 (ICAM1) and vascular cell adhesion molecule 1 (VCAM1) in siSMAD7 cells, and MMP9 expression. In amnion, siSMAD7 cells treated with IL1B also decreased cytokine and chemokine production, ICAM1 and MMP9 expression. In conclusion, we report a proinflammatory role for SMAD7 in human gestational tissues, with SMAD7 silencing attenuating the inflammatory response.

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.

Knockdown of Smad7 With a Specific Antisense Oligonucleotide Attenuates Colitis and Colitis-Driven Colonic Fibrosis in Mice

BACKGROUND

In Crohn's disease (CD), the pathogenic immune response is associated with high Smad7, an inhibitor of TGF-β1 signaling. Smad7 knockdown with Mongersen, a specific antisense oligonucleotide-containing compound, restores TGF-β1 activity leading to inhibition of inflammatory signals and associates with clinical benefit in CD patients. As TGF-β1 is pro-fibrogenic, it remains unclear whether Mongersen-induced Smad7 inhibition increases the risk of intestinal fibrosis. We assessed the impact of Smad7 inhibition on the course of colitis-driven intestinal fibrosis in mice.

METHODS

BALB/c mice were rectally treated with increasing doses of trinitrobenzene sulfonic acid (TNBS) for 8 or 12 weeks. The effect of oral Smad7 antisense or control oligonucleotide, administered to mice starting from week 5 or week 8, respectively, on mucosal inflammation and colitis-associated colonic fibrosis was assessed. Mucosal samples were analyzed for Smad7 by immunoblotting and immunohistochemistry, TGF-β1 by enzyme-linked immunosorbent assay, and collagen by immunohistochemistry.

RESULTS

TNBS-induced chronic colitis was associated with colonic deposition of collagen I and fibrosis, which were evident at week 8 and became more pronounced at week 12. TNBS treatment enhanced Smad7 in both colonic epithelial and lamina propria mononuclear cells. Colitic mice treated with Smad7 antisense oligonucleotide exhibited reduced signs of colitis, less collagen deposition, and diminished fibrosis. These findings were associated with diminished synthesis of TGF-β1 and reduced p-Smad3 protein expression.

CONCLUSION

Attenuation of colitis with Smad7 antisense oligonucleotide limits development of colonic fibrosis.

Current, experimental, and future treatments in inflammatory bowel disease: a clinical review

Inflammatory bowel diseases (IBDs) may result from dysregulated mucosal immune responses directed toward the resident intestinal microbiota. This review describes the hallmark immunobiology of Crohn's disease and ulcerative colitis as well as therapeutic targets and mechanisms of action for current, experimental, and future treatments in IBD. Conventional therapies include 5-aminosalicylic acid, glucocorticosteroids, thiopurines, and methotrexate. Since 1997, monoclonal antibodies have gained widespread use. These consist of antibodies directed against pro-inflammatory cytokines such as tumor necrosis factor α, interleukin (IL)-12, and IL-23, or anti-homing antibodies directed against α4β7 integrin. Emerging oral therapies include modulators of intracellular signal transduction such as Janus kinase inhibitors. Vitamin D may help to regulate innate and adaptive immune responses. Modulation of the intestinal microbiota, using live microorganisms (probiotics), substrates for the colonic microbiota (prebiotics), or fecal microbiota transplantation (FMT), is in development. Dietary supplements are in widespread use, but providing evidence for their benefit is challenging. Stem cell treatment and nervous stimulation are promising future treatments.

Differential Expression of microRNAs in Peripheral Blood Mononuclear Cells Identifies Autophagy and TGF-Beta-Related Signatures Aberrantly Expressed in Inflammatory Bowel Disease

BACKGROUND AND AIMS

MicroRNAs [miRNAs] have emerged as important regulators in inflammatory bowel disease [IBD]. This study investigated differential expression of miRNAs across clinical phenotypes in a well-characterized cohort of IBD patients and healthy controls [HCs].

METHODS

A cohort of Crohn's disease [CD] and ulcerative colitis [UC] patients and HCs was prospectively accrued. Total RNA was extracted from peripheral blood mononuclear cells for all subjects. miRNA expression was measured using NanoString technologies. The subjects were stratified according to disease activity and location. Statistical significance was assessed per miRNA across outcomes and corrected for multiple testing. miRNA regulation of transcription of important results was confirmed in vitro by a dual luciferase reporter assay and autophagy function was evaluated using immunofluorescence imaging of LC3 puncta in HeLa cells.

RESULTS

In total, 120 subjects were enrolled. Seventy-four miRNAs were differentially expressed across CD, UC and HCs. Comparing quiescent CD [CDq] with HCs we found ten miRNAs upregulated in CDq. When comparing colonic CD [CCD] to UC, seven miRNAs were upregulated in CCD. The most differentially expressed miRNA in CCD vs UC was miR-874-3p, and we showed its possible utility as a biomarker of differential diagnosis. We showed miR-874-3p targets ATG16L1 and reduces its expression in vitro. An miR-874-3p mimic dysregulates autophagy by a reduction of LC3 in vitro.

CONCLUSIONS

We identified unique miRNA signatures expressed in distinct IBD phenotypes. These associations highlight pathways dysregulated by aberrant miRNA expression, revealing possible mechanisms underlying the pathophysiology of IBD, but also suggest a cluster of miRNAs as readily accessible biomarkers to aid in differential diagnosis.

Why Drugs Fail in Late Stages of Development: Case Study Analyses from the Last Decade and Recommendations

New drug development is both resource and time intensive, where later clinical stages result in significant costs. We analyze recent late-stage failures to identify drugs where failures result from inadequate scientific advances as well as drugs where we believe pitfalls could have been avoided. These can be broadly classified into two categories: 1) where science is mature and the failures can be avoided through rigorous and prospectively determined decision-making criteria, scientific curiosity, and discipline to follow up on emerging findings; and 2) where problems encountered in Phase 3 failures cannot be explained at this time, as the science is not sufficiently advanced and companies/investigators need to recognize the possibility of deficiency of our knowledge. Through these case studies, key themes critical for successful drug development emerge-understanding the therapeutic pathway including receptor and signaling biology, pharmacological responses related to safety and efficacy, pharmacokinetics of the drug and exposure at target site, optimum dose, and dosing regimen; and identification of patient sub-populations likely to respond and will have a favorable benefit-risk profile, design of clinical trials, and a quantitative framework that can guide data-driven decision making. It is essential that the right studies are conducted early in the development process to answer the key questions, with the emphasis on learning in the early stages of development, whereas Phase 3 should be reserved for confirming the safety and efficacy. Utilization of innovative technology in identifying patients based on molecular signature of their disease, rapid assessment of pharmacological response, mechanistic modeling of emerging data, seamless operational processes to reduce start-up and wind-down time for clinical trials through use of electronic health records and data mining, and development of novel and objective clinical efficacy endpoints are some concepts for improving the success rate.

Human TGF-β1 deficiency causes severe inflammatory bowel disease and encephalopathy

Transforming growth factor (TGF)-β1 (encoded by TGFB1) is the prototypic member of the TGF-β family of 33 proteins that orchestrate embryogenesis, development and tissue homeostasis1,2. Following its discovery 3 , enormous interest and numerous controversies have emerged about the role of TGF-β in coordinating the balance of pro- and anti-oncogenic properties4,5, pro- and anti-inflammatory effects 6 , or pro- and anti-fibrinogenic characteristics 7 . Here we describe three individuals from two pedigrees with biallelic loss-of-function mutations in the TGFB1 gene who presented with severe infantile inflammatory bowel disease (IBD) and central nervous system (CNS) disease associated with epilepsy, brain atrophy and posterior leukoencephalopathy. The proteins encoded by the mutated TGFB1 alleles were characterized by impaired secretion, function or stability of the TGF-β1-LAP complex, which is suggestive of perturbed bioavailability of TGF-β1. Our study shows that TGF-β1 has a critical and nonredundant role in the development and homeostasis of intestinal immunity and the CNS in humans.

High SMAD7 and p-SMAD2,3 expression is associated with environmental enteropathy in children

Enteropathies such as Crohn's disease are associated with enteric inflammation characterized by impaired TGF-β signaling, decreased expression of phosphorylated (p)-SMAD2,3 and increased expression of SMAD7 (an inhibitor of SMAD3 phosphorylation). Environmental enteropathy (EE) is an acquired inflammatory disease of the small intestine (SI), which is associated with linear growth disruption, cognitive deficits, and reduced oral vaccine responsiveness in children <5 y in resource-poor countries. We aimed to characterize EE inflammatory pathways by determining SMAD7 and p-SMAD2,3 levels (using Western blotting) in EE duodenal biopsies (N = 19 children, 7 from Pakistan, 12 from Zambia) and comparing these with healthy controls (Ctl) and celiac disease (CD) patients from Italy. Densitometric analysis of immunoblots showed that EE SI biopsies expressed higher levels of both SMAD7 (mean±SD in arbitrary units [a.u.], Ctl = 0.47±0.20 a.u., EE = 1.13±0.25 a.u., p-value = 0.03) and p-SMAD2,3 (mean±SD, Ctl = 0.38±0.14 a.u., EE = 0.60±0.10 a.u., p-value = 0.03). Immunohistochemistry showed that, in EE, SMAD7 is expressed in both the epithelium and in mononuclear cells of the lamina propria (LP). In contrast, p-SMAD3 in EE is expressed much more prominently in epithelial cells than in the LP. The high SMAD7 immunoreactivity and lack of p-SMAD3 expression in the LP suggests defective TGF-β signaling in the LP in EE similar to a previously reported SMAD7-mediated inflammatory pathway in refractory CD and Crohn's disease. However, Western blot densitometry showed elevated p-SMAD2,3 levels in EE, possibly suggesting a different inflammatory pathway than Crohn's disease but more likely reflecting cumulative protein expression from across all compartments of the mucosa as opposed to the LP alone. Further studies are needed to substantiate these preliminary results and to illustrate the relationship between SMAD proteins, TGF-β signaling, and inflammatory cytokine production, all of which may be potential therapeutic targets.

Emerging oral targeted therapies in inflammatory bowel diseases: opportunities and challenges

To improve quality of life and prevent long-term risks in patients with inflammatory bowel diseases (IBDs: Crohn's disease, ulcerative colitis), it is essential to suppress inflammatory activity adequately. However, corticosteroids are only suitable for therapy of acute flares and the evidence for positive effects of immunosuppressive substances like azathioprine or 6-mercapropurine is mainly limited to maintenance of remission. In addition, only subgroups of patients benefit from biologicals targeting tumour necrosis factor α or α4β7 integrins. In summary, until now the disease activity is not sufficiently controlled in a relevant fraction of the patients with IBD. Thus, there is an urge for the development of new substances in the therapy of ulcerative colitis and Crohn's disease. Fortunately, new oral and parenteral substances are in the pipeline. This review will focus on oral substances, which have already passed phase II studies successfully at this stage. In this article, we summarize data regarding AJM300, phosphatidylcholine (LT-02), mongersen, ozanimod, filgotinib and tofacitinib. AJM300 and ozanimod were tested in patients with ulcerative colitis and target lymphocyte trafficking through inhibition of the α subunit of integrin, respectively binding to the sphingosine-1-phosphate receptor (subtypes 1 and 5) on lymphocytes. Mongersen was utilized in patients with Crohn's disease and accelerates the degradation of SMAD7 mRNA, which consequently strengthens the mainly anti-inflammatory signalling pathway of transforming growth factor β1. Various Janus kinase (JAK) inhibitors were developed, which inhibit the intracellular signalling pathway of cytokines. For example, the JAK1 blocker filgotinib was tested in Crohn's disease, whereas the JAK1/3 inhibitor tofacitinib was tested in clinical trials for both Crohn's disease and ulcerative colitis. A different therapeutic approach is the substitution of phosphatidylcholine (LT-02), which might recover the colonic mucus. Taken together, clinical trials with these new agents have opened avenues for further clinical studies and it can be expected that at least some of these agents will be finally approved for clinical therapy.

Janus Kinase Antagonists and Other Novel Small Molecules for the Treatment of Crohn's Disease

There is an ongoing, unmet need for effective therapies for Crohn's disease. Treatments for Crohn's disease continue to evolve from the traditional biologics to novel small molecules, with targeted mechanisms directed toward pathways that are dysregulated in Crohn's disease. There are multiple emerging mechanisms of action, including Janus kinase inhibition, Smad7 inhibition, and sphingosine-1-phosphate receptor modulators, that are administered as oral medications, and small molecules represent the next generation of therapies for Crohn's disease.

Regulation of the Immune Response by TGF-β: From Conception to Autoimmunity and Infection

Transforming growth factor β (TGF-β) is a pleiotropic cytokine involved in both suppressive and inflammatory immune responses. After 30 years of intense study, we have only begun to elucidate how TGF-β alters immunity under various conditions. Under steady-state conditions, TGF-β regulates thymic T-cell selection and maintains homeostasis of the naïve T-cell pool. TGF-β inhibits cytotoxic T lymphocyte (CTL), Th1-, and Th2-cell differentiation while promoting peripheral (p)Treg-, Th17-, Th9-, and Tfh-cell generation, and T-cell tissue residence in response to immune challenges. Similarly, TGF-β controls the proliferation, survival, activation, and differentiation of B cells, as well as the development and functions of innate cells, including natural killer (NK) cells, macrophages, dendritic cells, and granulocytes. Collectively, TGF-β plays a pivotal role in maintaining peripheral tolerance against self- and innocuous antigens, such as food, commensal bacteria, and fetal alloantigens, and in controlling immune responses to pathogens.

CCL20 Is Negatively Regulated by TGF-β1 in Intestinal Epithelial Cells and Reduced in Crohn's Disease Patients With a Successful Response to Mongersen, a Smad7 Antisense Oligonucleotide

BACKGROUND AND AIMS

The chemokine CCL20 is over-produced in epithelium of Crohn's disease [CD] patients and contributes to recruiting immune cells to inflamed gut. Tumour necrosis factor-α [TNF-α] is a powerful inducer of CCL20 in intestinal epithelial cells. In CD, high levels of Smad7 block the activity of transforming growth factor-β1 [TGF-β1], a negative regulator of TNF signalling. We investigated whether intestinal epithelial cell-derived CCL20 is negatively regulated by TGF-β1 and whether Smad7 knock-down reduces CCL20 in CD.

METHODS

CCL20 was evaluated in NCM460, a normal colonic epithelial cell line, stimulated with TGF-β1 and TNF-α, and in Smad7 over-expressing NCM460 cells. CCL20 and Smad7 expression were assessed in sections of CD intestinal specimens by immunochemistry, and in CD colonic explants treated with mongersen, a Smad7 antisense oligonucleotide. CCL20 was examined in serum samples taken from 95 of 166 active CD patients receiving mongersen or placebo for 2 weeks and participating in a phase II, multicentre, double-blind, placebo-controlled study.

RESULTS

CCL20 expression was increased by TNF-α, and this effect was inhibited by TGF-β1 in NCM460 cells, but not in Smad7 over-expressing NCM460 cells. In CD, epithelium CCL20 and Smad7 co-localised, and treatment of CD explants with mongersen reduced CCL20 production. During follow-up, in responders to mongersen, serum CCL20 levels significantly decreased, whereas patients without response/remission to mongersen and placebo patients did not have change in CCL20.

CONCLUSIONS

TGF-β1 reduces intestinal epithelial cell-derived CCL20 production, an effect abrogated by Smad7. CD patients responding to mongersen demonstrated a reduction in serum CCL20.

[Role of Inhibitory Transforming Growth Factor-β Signal Smad7 in Helicobacter pylori-associated Gastric Damage]

Background/Aims

Transforming growth factor-beta (TGF-β) is a cytokine implicated in the susceptibility, development, and progression of gastrointestinal cancer and certain other neoplasms. In the later stages of cancer, TGF-β not only acts as a bystander of host-immune response, but also contributes to cell growth, invasion, and metastasis. In the current study, we generated gastric mucosal cells that stably express Smad7, and explored the Helicobacter pylori-associated biological changes between mock-transfected and Smad7-transfected RGM1 cells.

Methods

RGM1 cells stably transfected with Smad7 were infected with H. pylori, and molecular changes in apoptotic markers and inflammatory mediators were examined. Several candidate genes were explored in Smad7-overexpressing cells after H. pylori infection.

Results

Overexpression of Smad7 in RGM1 cells significantly increased the H. pylori-induced cytotoxicity compared to mock-transfected cells. Exaggerated increases in inflammatory mediators, cyclooxygenase 2, inducible NO synthase, and augmented apoptosis were noted in Smad7-overexpressing cells, whereas mitigated heme oxygenase 1 was noted in Smad7- overexpressing cells. These phenomena were reversed in cells transfected with Smad7 siRNA.

Conclusions

These data suggest that inhibition of Smad7 is a possible target for mitigating H. pylori-associated inflammation.

Genetic risk variants as therapeutic targets for Crohn's disease

The pathogenesis of Inflammatory bowel diseases (IBD) is multifactorial, with interactions between genetic and environmental factors. Despite the existence of genetic factors being largely demonstrated by epidemiological data and several genetic studies, only a few findings have been useful in term of disease prediction, disease progression and targeting therapy. Areas covered: This review summarizes the results of genome-wide association studies in Crohn's disease, the role of epigenetics and the recent discovery by genetic studies of new pathogenetic pathways. Furthermore, it focuses on the importance of applying genetic data to clinical practice, and more specifically how to better target therapy and predict potential drug-related toxicity. Expert opinion: Some genetic markers identified in Crohn`s disease have allowed investigators to hypothesize about, and in some cases, prove the usefulness of new specific therapeutic agents. However, the heterogeneity and complexity of this disease has so far limited the daily clinical use of genetic information. Finally, the study of the implications of genetics on therapy, either to predict efficacy or avoid toxicity, is considered still to be in its infancy.

Lessons Learned From Trials Targeting Cytokine Pathways in Patients With Inflammatory Bowel Diseases

Insights into the pathogenesis of inflammatory bowel diseases (IBDs) have provided important information for the development of therapeutics. Levels of interleukin 23 (IL23) and T-helper (Th) 17 cell pathway molecules are increased in inflamed intestinal tissues of patients with IBD. Loss-of-function variants of the IL23-receptor gene (IL23R) protect against IBD, and, in animals, blocking IL23 reduces the severity of colitis. These findings indicated that the IL23 and Th17 cell pathways might be promising targets for the treatment of IBD. Clinical trials have investigated the effects of agents designed to target distinct levels of the IL23 and Th17 cell pathways, and the results are providing insights into IBD pathogenesis and additional strategies for modulating these pathways. Strategies to reduce levels of proinflammatory cytokines more broadly and increase anti-inflammatory mechanisms also are emerging for the treatment of IBD. The results from trials targeting these immune system pathways have provided important lessons for future trials. Findings indicate the importance of improving approaches to integrate patient features and biomarkers of response with selection of therapeutics.

Sodium chloride-enriched Diet Enhanced Inflammatory Cytokine Production and Exacerbated Experimental Colitis in Mice

BACKGROUND AND AIM

Environmental factors are supposed to play a decisive role in the pathogenesis of inflammatory bowel diseases [IBDs]. Increased dietary salt intake has been linked with the development of autoimmune diseases, but the impact of a salt-enriched diet on the course of IBD remains unknown. In this study, we examined whether high salt intake alters mucosal cytokine production and exacerbates colitis.

METHODS

Normal intestinal lamina propria mononuclear cells [LPMCs] were activated with anti-CD3/CD28 in the presence or absence of increasing concentrations of sodium chloride [NaCl] and/or SB202190, a specific inhibitor of p38/MAP Kinase. For in vivo experiments, a high dose of NaCl was administered to mice 15 days before induction of trinitrobenzene-sulfonic acid [TNBS]-colitis or dextran sulfate sodium [DSS]-colitis. In parallel, mice were given SB202190 before induction of TNBS-colitis. Transcription factors and effector cytokines were evaluated by flow-cytometry and real-time PCR.

RESULTS

IL-17A, IL-23R, TNF-α, and Ror-γT were significantly increased in human LPMCs following NaCl exposure, while there was no significant change in IFN-γ, T-bet or Foxp3. Pharmacologic inhibition of p38/MAPK abrogated the NaCl-inducing effect on LPMC-derived cytokines. Mice receiving the high-salt diet developed a more severe colitis than control mice, and this effect was preventable by SB202190.

CONCLUSIONS

Our data indicated that exposure of intestinal mononuclear cells to a high-NaCl diet enhanced effector cytokine production and contributed to the exacerbation of experimental colitis in mice.

Emerging biologics in inflammatory bowel disease

Early biologic therapy is recommended in patients with inflammatory bowel disease and poor prognostic factors and in those refractory to conventional medications. Anti-tumor necrosis factor (anti-TNF) agents are the most commonly used biologic agents. However, some patients may not have an initial response to anti-TNF therapy, and one-third will develop loss of response over time. Anti-TNF drugs can also be associated with side effects. In addition, the use of biologics is currently limited by their cost, especially in developing countries. A number of new therapeutic targets, including novel small molecules, and cellular therapy are available or under investigation. These novel molecules include oral Janus kinase (JAK) inhibitor (tofacitinib), interleukin inhibitor (ustekinumab), oral SMAD7 antisense oligonucleotide (mongersen), and anti-integrin inhibitors (vedolizumab). Here, we review the mechanisms of action, the efficacy, and the safety data of these novel agents. Biological products that are highly similar to reference biologic products whose patents have expired-also known as "biosimilars"-can be produced at lower cost with similar efficacy, and are also available for the treatment of IBD. We review the efficacy data for such agents as well.

An Overview of the Innate and Adaptive Immune System in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) are thought to develop as a result of complex interactions between host genetics, the immune system and the environment including the gut microbiome. Although an improved knowledge of the immunopathogenesis of IBDs has led to great advances in therapy such as the highly effective anti-tumor necrosis factor class of medications, a significant proportion of patients with Crohn's disease and ulcerative colitis do not respond to anti-tumor necrosis factor antibodies. Further understanding of the different immune pathways involved in the genesis of chronic intestinal inflammation is required to help find effective treatments for IBDs. In this review, the role of the mucosal innate and adaptive immune system in IBD is summarized, highlighting new areas of discovery which may hold the key to identifying novel predictive or prognostic biomarkers and new avenues of therapeutic discovery.

High Smad7 sustains inflammatory cytokine response in refractory coeliac disease

Refractory coeliac disease (RCD) is a form of coeliac disease (CD) resistant to gluten-free diet and associated with elevated risk of complications. Many effector cytokines over-produced in the gut of patients with RCD are supposed to amplify the tissue-destructive immune response, but it remains unclear if the RCD-associated mucosal inflammation is sustained by defects in counter-regulatory mechanisms. The aim of the present study was to determine whether RCD-related inflammation is marked by high Smad7, an intracellular inhibitor of transforming growth factor-β₁ (TGF-β₁ ) activity. Smad7 was evaluated in duodenal biopsy samples of patients with RCD, patients with active CD, patients with inactive CD and healthy controls by Western blotting, immunohistochemistry and real-time PCR. In the same samples, TGF-β₁ and phosphorylated (p)-Smad2/3 were evaluated by ELISA and immunohistochemistry, respectively. Pro-inflammatory cytokine expression was evaluated in RCD samples cultured with Smad7 sense or antisense oligonucleotide. Smad7 protein, but not RNA, expression was increased in RCD compared with active and inactive CD patients and healthy controls and this was associated with defective TGF-β₁ signalling, as marked by diminished p-Smad2/3 expression. TGF-β₁ protein content did not differ among groups. Knockdown of Smad7 in RCD biopsy samples reduced interleukin-6 and tumour necrosis factor-α expression. In conclusion, in RCD, high Smad7 associates with defective TGF-β₁ signalling and sustains inflammatory cytokine production. These results indicate a novel mechanism by which the mucosal cytokine response is amplified in RCD and suggest that targeting Smad7 can be therapeutically useful in RCD.

Inflammatory bowel disease: exploring gut pathophysiology for novel therapeutic targets

Ulcerative colitis and Crohn's disease are the 2 major phenotypes of inflammatory bowel disease (IBD), which are influenced by a complex interplay of immunological and genetic elements, though the precise etiology still remains unknown. With IBD developing into a globally prevailing disease, there is a need to explore new targets and a thorough understanding of the pathophysiological differences between the healthy and diseased gut could unearth new therapeutic opportunities. In this review, we provide an overview of the major aspects of IBD pathogenesis and thereafter present a comprehensive analysis of the gut pathophysiology leading to a discussion on some of the most promising targets and biologic therapies currently being explored. These include various gut proteins (CXCL-10, GATA-3, NKG2D, CD98, microRNAs), immune cells recruited to the gut (mast cells, eosinophils, toll-like receptors 2, 4), dysregulated proinflammatory cytokines (interleukin-6, -13, -18, -21), and commensal microbiota (probiotics and fecal microbiota transplantation). We also evaluate some of the emerging nonconventional therapies being explored in IBD treatment focusing on the latest developments in stem cell research, oral targeting of the gut-associated lymphoid tissue, novel anti-inflammatory signaling pathway targeting, adenosine deaminase inhibition, and the beneficial effects of antioxidant and nutraceutical therapies. In addition, we highlight the growth of biologics and their targets in IBD by providing information on the preclinical and clinical development of over 60 biopharmaceuticals representing the state of the art in ulcerative colitis and Crohn's disease drug development.

New and Evolving Immunotherapy in Inflammatory Bowel Disease

BACKGROUND

Crohn's disease and ulcerative colitis are chronic inflammatory disorders associated with a dysregulated adaptive and innate immune response to gut commensals in genetically susceptible individuals. The pathogenesis of inflammatory bowel disease is complex, and the disease is characterized by significant phenotypic and genotypic heterogeneity.

SUMMARY

The introduction of anti-TNF biologics has resulted in improved clinical outcomes in patients with severe and moderately severe disease, but the current treatment paradigm continues to depend on systemic immunosuppression (steroids and immunomodulators) and surgical intervention in a significant number of patients, underscoring a significant unmet need. More recently, a number of genetic and immunologic abnormalities have been unraveled including aberrant intestinal mucosal defense function, abnormal intestinal permeability, dysregulated bacterial antigen processing by macrophages and presentation to T cells, cellular immune regulation and signaling, cytokine production, and leukocyte trafficking.

KEY MESSAGES

Understanding these molecular mechanisms and effector pathways presents an opportunity for the development of new and improved targeted therapies.

Mongersen, an oral Smad7 antisense oligonucleotide, in patients with active Crohn's disease

In Crohn's disease (CD), the tissue-damaging inflammation is sustained by defects of counter-regulatory mechanisms, which normally inhibit immune-inflammatory signals and promote repair of mucosal injury. In particular, in inflamed gut of CD patients there are elevated levels of Smad7, an intracellular protein that inhibits the function of transforming growth factor (TGF)-β1. Knockdown of Smad7 with a specific antisense oligonucleotide, named mongersen, restores TGF-β1 activity thus leading to suppression of inflammatory pathways and resolution of colitis in mice. Consistently, oral administration of mongersen to patients with active CD induces clinical remission. In this article, we review the available data supporting the pathogenic role of Smad7 in CD and discuss the results of recent phase I and II trials assessing the efficacy and safety of mongersen in CD patients.

Stem Cells in the Intestine: Possible Roles in Pathogenesis of Irritable Bowel Syndrome

Irritable bowel syndrome is one of the most common functional gastrointestinal (GI) disorders that significantly impair quality of life in patients. Current available treatments are still not effective and the pathophysiology of this condition remains unclearly defined. Recently, research on intestinal stem cells has greatly advanced our understanding of various GI disorders. Alterations in conserved stem cell regulatory pathways such as Notch, Wnt, and bone morphogenic protein/TGF-β have been well documented in diseases such as inflammatory bowel diseases and cancer. Interaction between intestinal stem cells and various signals from their environment is important for the control of stem cell self-renewal, regulation of number and function of specific intestinal cell types, and maintenance of the mucosal barrier. Besides their roles in stem cell regulation, these signals are also known to have potent effects on immune cells, enteric nervous system and secretory cells in the gut, and may be responsible for various aspects of pathogenesis of functional GI disorders, including visceral hypersensitivity, altered gut motility and low grade gut inflammation. In this article, we briefly summarize the components of these signaling pathways, how they can be modified by extrinsic factors and novel treatments, and provide evidenced support of their roles in the inflammation processes. Furthermore, we propose how changes in these signals may contribute to the symptom development and pathogenesis of irritable bowel syndrome.

Smad7 Knockdown Restores Aryl Hydrocarbon Receptor-mediated Protective Signals in the Gut

BACKGROUND AND AIM

In Crohn's disease [CD], the pathological process is driven by an excessive immune response that is poorly counterbalanced by regulatory mechanisms. One such a mechanism involves aryl hydrocarbon receptor [AhR], a transcription factor that delivers protective signals in the gut. Expression of AhR is reduced in CD lamina propria mononuclear cells [LPMC] even though factors accounting for such a defect remain unknown. Since CD LPMC express elevated levels of Smad7, an inhibitor of transforming growth factor beta 1 [TGF-β1] activity, and TGF-β1 regulates AhR in other systems, we examined the link between AhR and Smad7 in the gut.

METHODS

AhR and interleukin [IL]-22 were evaluated in normal LPMC stimulated with TGF-β1 and 6-formylindolo[3,2-b]carbazole [Ficz], an activator of AhR, and in CD LPMC incubated with a Smad7 antisense oligonucleotide and then stimulated with Ficz and TGF-β1. AhR and IL-22 expression was evaluated in LPMC of Smad7-transgenic mice. Finally, we evaluated the protective effect of Ficz on colitis in RAG1 mice injected with naïve or Smad7-overexpressing T cells.

RESULTS

In normal LPMC, TGF-β1 induced AhR and this event was associated with increased production of IL-22 following stimulation with Ficz. Treatment of CD LPMC with Smad7 antisense oligonucleotide enabled TGF-β1 to enhance AhR expression. Consistently, AhR expression and Ficz-induced IL-22 production were markedly reduced in T cells of Smad7-transgenic mice. In RAG1 mice, Ficz ameliorated colitis induced by wild type T cells but did not affect colitis induced by transfer of Smad7-overexpressing T cells.

CONCLUSIONS

The inverse correlation between Smad7 and AhR expression helps to propagate inflammatory signals in the gut.

The Role of Neuropeptides in Mouse Models of Colitis

Inflammatory bowel disease (IBD) constitutes an important clinically significant condition that results in morbidity and mortality. IBD can be generally classified into either ulcerative colitis (UC) or Crohn's disease (CD) that differs in the clinical and histopathology. The role of neuropeptides in the pathogenesis of these conditions is becoming increasingly recognized for their importance in modulating the inflammatory state. Animal models provide the greatest insight to better understand the pathophysiology of both disorders which will hopefully allow for improved treatment strategies. This review will provide a better understanding of the role of murine models for studying colitis.

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.

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.

Will novel oral formulations change the management of inflammatory bowel disease?

INTRODUCTION

The traditional management of inflammatory bowel disease (IBD) with sulphasalazine/5-aminosalicylic acid, glucocorticoids and immunomodulators (i.e., thiopurines and methotrexate) was nearly two decades ago extended with intravenously or subcutaneously administered biologics (i.e., tumor necrosis factor inhibitors and later gut-selective integrin antagonists). However, recently, orally administered treatments with simple, well-characterized, and stable structures consisting of either small molecules or anti-sense therapy have been devised.

AREAS COVERED

This review discusses the current approaches with promising new oral drugs with distinct modes of action, including: the Janus kinase inhibitors (i.e., tofacitinib, filgotinib and peficitinib); the immunomodulatory drug (laquinimod); a small α4 antagonist (AJM300); agonists for sphingosine-phosphate receptors (i.e., ozanimod, APD334, and amiselimod), as well as anti-sense therapy (mongersen) targeting SMAD7, drugs which directly target intracellular pathways of relevance for intestinal inflammation.

EXPERT OPINION

A new avenue using easily administered oral therapies for the management of IBD is being introduced. While their place in the clinical armamentarium remains to be proven, it is likely that many of these drugs will find their place in the treatment algorithm of IBD in the next few years. Thus, we will face times in which IBD therapy will be based on significantly more tablets than prescribed today.

Immunomodulators for the treatment of Crohn's disease in adults: optimal use and prospects for future drug treatments

Crohn's disease (CD) requires treatment beyond symptoms by enabling and maintaining mucosal healing and therefore clinical remission. However, with the increasing use of biologics there have been safety concerns and there is a significant cost implication with the early use of biologics. Therefore, it is imperative that patients with severe/complicated disease or poor prognostic factors are treated with an aggressive strategy while all remaining patients should be treated in a step-up strategy. The potential for disease modification with thiopurines and methotrexate is debated in CD when they are used as a monotherapy. In this review we discuss existing and newer therapies that have recently been developed for CD. We will also provide an algorithm for current management of adult CD patients in routine clinical practice.

TGF-β signaling is activated in patients with chronic HBV infection and repressed by SMAD7 overexpression after successful antiviral treatment

OBJECTIVES

Although animal studies demonstrated that Smad7 induction ameliorates TGF-β/SMAD-mediated fibrogenesis, its role in human hepatic diseases is rather obscure. Our study explored the activation status of TGF-β/activin pathway in patients with chronic liver diseases, and how it is affected by successful antiviral treatment in chronic HBV hepatitis (CHB).

METHODS

Thirty-seven CHB patients (19 with active disease, 14 completely remitted on long-term antiviral treatment and 4 with relapse after treatment withdrawal), 18 patients with chronic HCV hepatitis, 12 with non-alcoholic fatty liver disease (NAFLD), and 3 controls were enrolled in the study. Liver mRNA levels of CTGF, all TGF-β/activin isoforms, their receptors and intracellular mediators (SMADs) were evaluated using qRT-PCR and were correlated with the grade of liver inflammation and fibrosis staging. The expression and localization of pSMAD2 and pSMAD3 were assessed by immunohistochemistry.

RESULTS

TGF-β signalling is activated in CHB patients with active disease, while SMAD7 is up-regulated during the resolution of inflammation after successful treatment. SMAD7 overexpression was also observed in NAFLD patients exhibiting no or minimal fibrosis, despite the activation of TGF-β/activin signaling.

CONCLUSIONS

SMAD7 overexpression might represent a mechanism limiting TGF-β-mediated fibrogenesis in human hepatic diseases; therefore, SMAD7 induction likely represents a candidate for novel therapeutic approaches.

Antisense approach to inflammatory bowel disease: prospects and challenges

Despite the great success of anti-tumour necrosis factor-based therapies, the treatment of Crohn's disease (CD) and ulcerative colitis (UC) still remains a challenge for clinicians, as these drugs are not effective in all patients, their efficacy may wane with time, and their use can increase the risk of adverse events and be associated with the development of new immune-mediated diseases. Therefore, new therapeutic targets are currently being investigated both in pre-clinical studies and in clinical trials. Among the technologies used to build new therapeutic compounds, the antisense oligonucleotide (ASO) approach is slowly gaining space in the field of inflammatory bowel diseases (IBDs), and three ASOs have been investigated in clinical trials. Systemic administration of alicaforsen targeting intercellular adhesion molecule-1, a protein involved in the recruitment of leukocytes to inflamed intestine, was not effective in CD, even though the same compound was of benefit when given as an enema to UC patients. DIMS0150, targeting nuclear factor (NF) κB-p65, a transcription factor that promotes pro-inflammatory responses, was very promising in pre-clinical studies and is currently being tested in clinical trials. Oral mongersen, targeting Smad7, an intracellular protein that inhibits transforming growth factor (TGF)-β1 activity, was safe and well tolerated by CD patients, and the results of a phase II clinical trial showed the efficacy of the drug in inducing clinical remission in patients with active disease. In this leading article, we review the rationale and the clinical data available regarding these three agents, and we discuss the challenge of using ASOs in IBD.

The TGF-β/Smad System in IBD Pathogenesis

In Crohn's disease and ulcerative colitis, the tissue-damaging destructive immune response is sustained by defects of counterregulatory mechanisms, which normally attenuate inflammatory pathways and promote repair of mucosal injury. One such mechanism involves transforming growth factor-β1 (TGF-β1), a cytokine that is produced by multiple cell types and targets both immune and nonimmune cells. Both in vitro and in vivo studies strongly support the role of TGF-β1 as a negative regulator of mucosal inflammation and indicate that defective production/activity of this cytokine can lead to the development of or exacerbate colitis. Interestingly, in the inflamed intestine of patients with inflammatory bowel disease, TGF-β1 expression is upregulated but TGF-β1-mediated immunosuppression is markedly impaired because of high Smad7, an intracellular inhibitor of TGF-β1-associated signaling. Consistently, knockdown of Smad7 with a specific antisense oligonucleotide restores TGF-β1 activity, thus leading to decreased production of inflammatory cytokines in both colitic mice and inflammatory bowel disease patients and attenuates clinical activity in Crohn's disease patients. In this article, we review data supporting the role of Smad7 in the pathogenesis of inflammatory bowel disease and discuss whether inhibition of Smad7 is therapeutically useful in Crohn's disease and how the benefit/risk of such an intervention should be monitored in the patients.

Therapeutic innovations in inflammatory bowel diseases

Inflammatory bowel disease (IBD) is a spectrum of complex multifactorial immune disorders characterized by chronic inflammation of the gut. Significant advances have been made in unraveling the pathogenesis of this disease spectrum, which have spurred the discovery of new therapeutic targets and strategies. In this review, we highlight the emerging new classes of IBD therapeutics under clinical evaluation and their method of action, including JAK inhibitors, anti-SMAD7 oligonucleotides, and cell-based therapies. Moreover, we discuss how an approach based on unique molecular insights in a given patient will, in the future, lead to a truly individualized/tailored disease management, starting at diagnosis, aiding in prognosis, and resulting in a personalized therapeutic approach.

miR-195 plays a role in steroid resistance of ulcerative colitis by targeting Smad7

An imbalance in pro- and anti-inflammation is an important mechanism of steroid resistance in UC (ulcerative colitis), and miRNAs may participate in this process. The present study aimed to explore whether miRNAs play a role in the steroid resistance of UC by regulating gene expression of the inflammation signal pathway. SS (steroid-sensitive) patients, SR (steroid-resistant) patients and healthy individuals were recruited. In vivo miRNA profiles of serum samples showed that miR-195 was decreased significantly in the SR group compared with the SS group (P<0.05). This result was confirmed by qPCR (quantitative real-time PCR) and miRNA ISH (in situ hybridization) in serum and colon tissue samples. Online software was used to identify Smad7 mRNA as a potential target of miR-195. The direct interaction of miR-195 and Smad7 mRNA was investigated using a biotinylated miR-195 pull-down assay. Overexpression of a miR-195 precursor lowered cellular levels of Smad7 protein; conversely, antagonism of miR-195 enhanced Smad7 translation without disturbing Smad7 mRNA levels. A luciferase reporter assay revealed a repressive effect of miR-195 via a single Smad7 3'-UTR target site, and point mutation of this site prevented miR-195-induced repression of Smad7 translation. Furthermore, increased levels of miR-195 led to a decrease in c-Jun and p65 expression. In contrast, transfection with anti-miR-195 led to increased levels of c-Jun and p65 protein. The decrease in miR-195 led to an increase in Smad7 expression and corresponding up-regulation of p65 and the AP-1 (activator protein 1) pathway, which might explain the mechanism of steroid resistance in UC patients.

Dual TNF-α/IL-12p40 Interference as a Strategy to Protect Against Colitis Based on miR-16 Precursors With Macrophage Targeting Vectors

Cytokines are central components of the mucosal inflammatory responses that take place during the development of Crohn's disease. Cell-specific combination therapies against cytokines may lead to increased efficacy and even reduced side effects. Therefore, a colonic macrophage-specific therapy using miR-16 precursors that can target both TNF-α and IL-12p40 was tested for its efficacy in experimental colitic mice. Galactosylated low molecular weight chitosan (G-LMWC) associated with miR-16 precursors were intracolonically injected into mice. The cellular localization of miR-16 precursors was determined. The therapeutic effects and possible mechanism were further studied in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitic mice. The results show that specific upregulation of miR-16 level in colonic macrophages significantly reduces TNF-α and IL-12p40 expression, which could suppress the associated mucosal inflammation and ultimately result in the relief of colitic symptoms. This strategy, based on the dual silencing of colonic macrophage-specific cytokines, represents a potential therapeutic approach that may be valuable for colitis therapy.