Growth factors in inflammatory bowel disease

Therapeutic potential of the secreted Kazal-type serine protease inhibitor SPINK4 in colitis

Mucus injury associated with goblet cell (GC) depletion constitutes an early event in inflammatory bowel disease (IBD). Using single-cell sequencing to detect critical events in mucus dysfunction, we discover that the Kazal-type serine protease inhibitor SPINK4 is dynamically regulated in colitic intestine in parallel with disease activities. Under chemically induced colitic conditions, the grim status in Spink4-conditional knockout mice is successfully rescued by recombinant murine SPINK4. Notably, its therapeutic potential is synergistic with existing TNF-α inhibitor infliximab in colitis treatment. Mechanistically, SPINK4 promotes GC differentiation using a Kazal-like motif to modulate EGFR-Wnt/β-catenin and -Hippo pathways. Microbiota-derived diacylated lipoprotein Pam2CSK4 triggers SPINK4 production. We also show that monitoring SPINK4 in circulation is a reliable noninvasive technique to distinguish IBD patients from healthy controls and assess disease activity. Thus, SPINK4 serves as a serologic biomarker of IBD and has therapeutic potential for colitis via intrinsic EGFR activation in intestinal homeostasis.

An injectable subcutaneous colon-specific immune niche for the treatment of ulcerative colitis

As a chronic autoinflammatory condition, ulcerative colitis is often managed via systemic immunosuppressants. Here we show, in three mouse models of established ulcerative colitis, that a subcutaneously injected colon-specific immunosuppressive niche consisting of colon epithelial cells, decellularized colon extracellular matrix and nanofibres functionalized with programmed death-ligand 1, CD86, a peptide mimic of transforming growth factor-beta 1, and the immunosuppressive small-molecule leflunomide, induced intestinal immunotolerance and reduced inflammation in the animals' lower gastrointestinal tract. The bioengineered colon-specific niche triggered autoreactive T cell anergy and polarized pro-inflammatory macrophages via multiple immunosuppressive pathways, and prevented the infiltration of immune cells into the colon's lamina propria, promoting the recovery of epithelial damage. The bioengineered niche also prevented colitis-associated colorectal cancer and eliminated immune-related colitis triggered by kinase inhibitors and immune checkpoint blockade.

From the updated landscape of the emerging biologics for IBDs treatment to the new delivery systems

Inflammatory bowel diseases (IBDs) treatments have shifted from small-molecular therapeutics to the oncoming biologics. The first-line biologics against the moderate-to-severe IBDs are mainly involved in antibodies against integrins, cytokines and cell adhesion molecules. Besides, other biologics including growth factors, antioxidative enzyme, anti-inflammatory peptides, nucleic acids, stem cells and probiotics have also been explored at preclinical or clinical studies. Biologics with variety of origins have their unique potentials in attenuating immune inflammation or gut mucosa healing. Great advances in use of biologics for IBDs treatments have been archived in recent years. But delivering issues for biologic have also been confronted due to their liable nature. In this review, we will focus on biologics for IBDs treatments in the recent publications; summarize the current landscapes of biologics and their promise to control disease progress. Alternatively, the confronted challenges for delivering biologics will also be analyzed. To combat these drawbacks, some new delivering strategies are provided: firstly, designing the functional materials with high affinity toward biologics; secondly, the delivering vehicle systems to encapsulate the liable biologics; thirdly, the topical adhering delivery systems as enema. To our knowledge, this review is the first study to summarize the updated usage of the oncoming biologics for IBDs, their confronted challenges in term of delivery and the potential combating strategies.

Lack of Association between Epidermal Growth Factor or Its Receptor and Reflux Esophagitis, Barrett’s Esophagus, and Esophageal Adenocarcinoma: A Case-Control Study

The epidermal growth factor (EGF) and its receptor (EGFR) gene-gene interactions were shown to increase the susceptibility to esophageal cancer. However, the role of the EGF/EGFR pathway in the development of gastroesophageal reflux disease (GERD) and its complications (reflux esophagitis (RE), Barrett's esophagus (BE), and esophageal adenocarcinoma (EAC)) remains unclear. This association study is aimed at investigating functional EGF and EGFR gene polymorphisms, their mRNA expression in esophageal tissues, and EGF plasma levels in relation to RE, BE, and EAC development in the Central European population. 301 patients with RE/BE/EAC (cases) as well as 98 patients with nonerosive reflux disease (NERD) and 8 healthy individuals (controls) were genotyped for +61 A>G EGF (rs4444903) and +142285 G>A EGFR (rs2227983) polymorphisms using the TaqMan quantitative polymerase chain reaction (qPCR). In random subgroups, the EGF and EGFR mRNA expressions were analyzed by reverse transcription qPCR in esophageal tissue with and without endoscopically visible pathological changes; and the EGF plasma levels were determined by enzyme-linked immunosorbent assay. None of the genotyped SNPs nor EGF-EGFR genotype interactions were associated with RE, BE, or EAC development (p > 0.05). Moreover, mRNA expression of neither EGF nor EGFR differed between samples of the esophageal tissue with and without endoscopically visible pathology (p > 0.05) nor between samples from patients with different diagnoses, i.e., RE, BE, or EAC (p > 0.05). Nevertheless, the lower EGF mRNA expression in carriers of combined genotypes AA +61 EGF (rs4444903) and GG +142285 EGFR (rs2227983; p < 0.05) suggests a possible direct/indirect effect of EGF-EGFR gene interactions on EGF gene expression. In conclusion, EGF and EGFR gene variants and their mRNA/protein expression were not associated with RE, BE or EAC development in the Central European population.

FOXP3 variants are independently associated with transforming growth factor Β1 plasma levels in female patients with inflammatory bowel disease

OBJECTIVE

The aim of this study was to evaluate the association of -924 G>A (rs2232365) and -3279 C>A (rs3761548) FOXP3 variants with IBD susceptibility, clinical and endoscopic activity, and IL-10 and TGF-β1 plasma levels.

METHOD

The study included 110 IBD female patients, 60 with Ulcerative Colitis (UC) and 50 with Crohn's Disease (CD), and 154 female controls. FOXP3 variants were determined with Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). Plasma levels of IL-10 and TGF-β1 were determined using immunofluorimetric assay.

RESULTS

AA genotype of rs2232365 and rs3761548 was associated with CD (OR = 3.147, 95% CI 1.015-9.758, p = 0.047) and UC (OR = 3.221, 95% CI 1.050-9.876, p = 0.041) susceptibility, respectively. However, were not associated with TGF-β1 and IL-10 levels, and endoscopic/clinical activity disease. GAGA haplotype was associated with IBD (OR = 4.003, 95% CI 1.100-14.56, p = 0.035) and UC susceptibility (OR = 6.107, 95% CI 1.609-23.18, p = 0.008). In addition, IBD patients with the GAGA haplotype had lower TGF-β1 levels (p = 0.041). Moreover, G/C haplotype (dominant model) had a protective effect of 60% in CD susceptibility and lower Endoscopic Severity Index.

CONCLUSIONS

These results suggest that FOXP3 variants could exert a role in the Treg, which could be one of the factors involved in the susceptibility and pathogenesis of IBD.

Vascular endothelial growth factor, endostatin levels and clinical features among patients with ulcerative colitis and irritable bowel syndrome and among healthy controls: a cross-sectional analytical study

BACKGROUND

Increased angiogenetic activity in inflammatory bowel disease (IBD) has been shown in previous studies. The aim of this study was to evaluate the relationship of serum vascular endothelial growth factor (VEGF) and endostatin levels with clinical features and mucosal expression in patients with ulcerative colitis (UC).

DESIGN AND SETTING

Cross-sectional analytical study conducted in a tertiary-level public hospital.

METHODS

Serum VEGF and endostatin levels were determined in 82 individuals: 39 with UC, 28 with irritable bowel syndrome (IBS) and 15 healthy controls (HCs), using enzyme-linked immunosorbent assays (ELISA). VEGF and endostatin expressions were studied using immunohistochemistry (IHC).

RESULTS

Mean serum VEGF and endostatin levels were significantly higher in patients with UC than in patients with IBS and in HCs (511.9 ± 377.5 pg/ml, 305.0 ± 121.42 pg/ml and 36.1 ± 40.6 pg/ml; P = 0.001 for VEGF; and 155.50 ± 59.8 ng/ml, 116.9 ± 23.8 ng/ml and 102.2 ± 22.4 ng/ml; P < 0.001 for endostatin, respectively). There was a positive correlation between serum VEGF and endostatin levels (r = 0.422; P < 0.01). Mean H-scores for VEGF expression were higher in the active UC group than in the inactive UC and IBS groups, in the stroma, endothelium and epithelium. Mean H-scores for endostatin expression were higher in the active UC group than in the inactive UC and IBS groups, in the stroma and endothelium. There was no endostatin expression in the epithelium.

CONCLUSION

Increased endostatin appears to be a defensive reaction to increased VEGF in patients with UC.

Dsg2 via Src-mediated transactivation shapes EGFR signaling towards cell adhesion

Rapidly renewing epithelial tissues such as the intestinal epithelium require precise tuning of intercellular adhesion and proliferation to preserve barrier integrity. Here, we provide evidence that desmoglein 2 (Dsg2), an adhesion molecule of desmosomes, controls cell adhesion and proliferation via epidermal growth factor receptor (EGFR) signaling. Dsg2 is required for EGFR localization at intercellular junctions as well as for Src-mediated EGFR activation. Src binds to EGFR and is required for localization of EGFR and Dsg2 to cell-cell contacts. EGFR is critical for cell adhesion and barrier recovery. In line with this, Dsg2-deficient enterocytes display impaired barrier properties and increased cell proliferation. Mechanistically, Dsg2 directly interacts with EGFR and undergoes heterotypic-binding events on the surface of living enterocytes via its extracellular domain as revealed by atomic force microscopy. Thus, our study reveals a new mechanism by which Dsg2 via Src shapes EGFR function towards cell adhesion.

Phosphorylation of Ser-525 in βPix impairs Nox1-activating ability in Caco-2 cells

βPix activates Nox1, an O₂^--generating NADPH oxidase, through Rac activation. In this study, we found that S525E mutation of βPix eliminated its Nox1-activating ability in transfected Caco-2 cells. Unexpectedly, affinity for Rac was not diminished but rather enhanced by S525E mutation, and guanine nucleotide exchange factor (GEF) activity was not altered. The N-terminal fragment (amino acids 1-400) showed similar Rac-binding and GEF activity to wild-type βPix. In contrast, the C-terminal fragment (amino acids 408-646) had higher Rac-binding activity, particularly for Rac-GTP, than wild-type βPix, and showed no GEF activity. These data suggest that a second Rac-binding site within the C-terminal region is opened by phosphorylation of Ser-525. The site may bind not only Rac-GDP but also Rac-GTP released from the N-terminal catalytic region, which interrupts Rac-GTP translocation to the membrane where Nox1 resides. If one considers that S340E mutation enhances Nox1 activation (Kaito et al., 2014), the present study suggests that βPix can also play an inhibitory role in O₂^- production, depending on the sites of phosphorylation.

Green Tea Induced Cellular Proliferation and the Expression of Transforming Growth Factor-β1 in the Jejunal Mucosa of Fasting Rats

OBJECTIVE

The aim of this study was to understand whether or not the protective effect of green tea after fasting-induced damage in the jejunal mucosa of rat is dependent on cell proliferation and the stimulation of specific growth factors.

MATERIALS AND METHODS

Sixty adult male Wistar rats were used in this study. The animals were divided randomly into 5 groups, with 12 in each group (G1-5). The animals in G1 (control group) were fed a rat chow diet and water ad libitum. The animals in G2 (fasting group) were fasted for 3 days. The animals in the G3, G4, and G5 groups were fasted for 3 days as G2, but were given water (G3), green tea (G4), or a vitamin E (G5) solution, respectively, for another 7 days. The animals were euthanized, and the jejunum was removed and processed for histological and immunohistochemical analysis.

RESULTS

Compared to the G3 group, the jejunal mucosa of G4 rats showed a 70.6% higher level (p < 0.001) of expression of proliferating cell nuclear antigen and 98% higher level (p = 0.0001) of the expression of transforming growth factor-β1 (TGF-β1), whereas the level of fibroblast growth factor-1 (FGF-1) and insulin-like growth factor-1 (IGF-1) expression was 22 and 11% lower, respectively, in G4 animals as compared to G3 rats. These differences in the expression of FGF-1 and IGF-1 in G4 animals were not statistically significant.

CONCLUSION

In this study, green tea repaired the fasting-induced damage in the jejunal mucosa of rats, mainly by inducing a significant expression of TGF-β1 in the jejunal mucosa.

Endogenous and exogenous control of gastrointestinal epithelial function: building on the legacy of Bayliss and Starling

Transport of fluid and electrolytes in the intestine allows for appropriate adjustments in luminal fluidity while reclaiming water used in digesting and absorbing a meal, and is closely regulated. This article discusses various endogenous and exogenous mechanisms whereby transport is controlled in the gut, placing these in the context of the ideas about the neurohumoral control of alimentary physiology that were promulgated by William Bayliss and Ernest Starling. The article considers three themes. First, mechanisms that intrinsically regulate chloride secretion, centred on the epidermal growth factor receptor (EGFr), are discussed. These may be important in ensuring that excessive chloride secretion, with the accompanying loss of fluid, is not normally stimulated by intestinal distension as the meal passes through the gastrointestinal tract. Second, mechanisms whereby probiotic microorganisms can impart beneficial effects on the gut are described, with a focus on targets at the level of the epithelium. These findings imply that the commensal microbiota exert important influences on the epithelium in health and disease. Finally, mechanisms that lead to diarrhoea in patients infected with an invasive pathogen, Salmonella, are considered, based on recent studies in a novel mouse model. Diarrhoea is most likely attributable to reduced expression of absorptive transporters and may not require the influx of neutrophils that accompanies infection. Overall, the goal of the article is to highlight the many ways in which critical functions of the intestinal epithelium are regulated under physiological and pathophysiological conditions, and to suggest possible targets for new therapies for digestive disease states.

Interferon-driven alterations of the host's amino acid metabolism in the pathogenesis of typhoid fever

Enteric fever, caused by Salmonella enterica serovar Typhi, is an important public health problem in resource-limited settings and, despite decades of research, human responses to the infection are poorly understood. In 41 healthy adults experimentally infected with wild-type S. Typhi, we detected significant cytokine responses within 12 h of bacterial ingestion. These early responses did not correlate with subsequent clinical disease outcomes and likely indicate initial host-pathogen interactions in the gut mucosa. In participants developing enteric fever after oral infection, marked transcriptional and cytokine responses during acute disease reflected dominant type I/II interferon signatures, which were significantly associated with bacteremia. Using a murine and macrophage infection model, we validated the pivotal role of this response in the expression of proteins of the host tryptophan metabolism during Salmonella infection. Corresponding alterations in tryptophan catabolites with immunomodulatory properties in serum of participants with typhoid fever confirmed the activity of this pathway, and implicate a central role of host tryptophan metabolism in the pathogenesis of typhoid fever.

Overexpression of miR-595 and miR-1246 in the sera of patients with active forms of inflammatory bowel disease

BACKGROUND

MicroRNAs (miRNAs) are dysregulated in the inflammatory bowel diseases, Crohn's disease (CD) and ulcerative colitis (UC), which arise due to dysfunctional host-microbe interactions and impairment of the barrier function of the intestine. Here, we sought to determine whether circulating miRNAs are biomarkers of active colonic CD and UC and can provide insights into disease pathogenesis. Comparison was made with serum miRNAs in patients with rheumatoid arthritis (RA).

METHODS

Total serum RNA from patients with colonic CD, UC, and RA, and normal healthy adults was screened for disease-associated miRNAs by microarray analysis, with subsequent validation by quantitative reverse-transcription polymerase chain reaction. MiRNA targets were identified by luciferase reporter assays.

RESULTS

MiR-595 and miR-1246 were significantly upregulated in the sera of active colonic CD, UC, and RA patients, compared with healthy subjects; and in active colonic CD and UC compared with inactive disease. Luciferase reporter assays indicated that miR-595 inhibits the expression of neural cell adhesion molecule-1 and fibroblast growth factor receptor 2.

CONCLUSIONS

Serum miR-595 and miR-1246 are biomarkers of active CD, UC, and RA. These findings gain significance from reports that miR-595 impairs epithelial tight junctions, whereas miR-1246 indirectly activates the proinflammatory nuclear factor of activated T cells. miR-595 targets the cell adhesion molecule neural cell adhesion molecule-1, and fibroblast growth factor receptor 2, which plays a key role in the differentiation, protection, and repair of colonic epithelium, and maintenance of tight junctions. miR-595 and miR-1246 warrant testing as potential targets for therapeutic intervention in the treatment of inflammatory bowel disease.

Altered chemokine signalling in endothelial progenitor cells from acute ulcerative colitis patients

Ulcerative colitis (UC) is a chronic, idiopathic, inflammatory bowel disease, characterized by alternating stages of clinically active and inactive disease. UC exhibits several inflammatory characteristics, including immune activation, leukocyte infiltration, and altered vascular density. In UC, many of the upregulated inflammatory cytokines are proangiogenic and are released by diverse cell populations, such as infiltrating immune cells and endothelial cells (EC). Increasing evidences suggest that neovascularisation may involve also endothelial progenitor cells (EPCs). In this study we evaluated EPCs recruitment and homing, assessed by CXCR4 expression, in both acute and remitting phase of UC. We report an overall decrease of EPCs in UC patients (controls = 97,94 ± 37,34 cells/mL; acute = 31,10 ± 25,38 cells/mL; remitting = 30,33 ± 19,02 cells/mL; P < 0.001 for both UC groups versus controls). Moreover CXCR4⁺-EPCs, committed to home in inflammatory conditions, were found to be reduced in acute UC patients compared to both remitting patients and controls (acute = 3,13 ± 4,61 cells/mL; controls = 20,12 ± 14,0; remitting = 19,47 ± 12,83; P < 0,001). Interestingly, we found that administration of anti-inflammatory drugs in acute UC is associated with an increase in circulating EPCs, suggesting that this therapy may exert a strong influence on the progenitor cells response to inflammatory processes.

Lipophilic modification enhances anti-colitic properties of rosmarinic acid by potentiating its HIF-prolyl hydroxylases inhibitory activity

Inhibition of hypoxia inducible factor-prolyl hydroxylase-2 (HPH), leading to activation of hypoxia inducible factor (HIF)-1 is a potential therapeutic strategy for the treatment of colitis. Rosmarinic acid (RA), an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid is a naturally occurring polyphenolic compound with two catechols, a or inhibition of HPH. To improve accessibility of highly hydrophilic RA to HPH, an intracellular target, RA was chemically modified to decrease hydrophilicity. Of the less-hydrophilic derivatives, rosmarinic acid methyl ester (RAME) most potently inhibited HPH. Accordingly, RAME prevented hydroxylation of HIF-1α and consequently stabilized HIF-1α protein in cells. RAME inhibition of HPH and induction of HIF-1α were diminished by elevated doses of the required factors of HPH, 2-ketoglutarate and ascorbate. RAME induction of HIF-1α led to activation of an ulcer healing pathway, HIF-1-vascular endothelial growth factor (VEGF), in human colon carcinoma cells. RAME administered rectally ameliorated TNBS-induced rat colitis and substantially decreased the levels of pro-inflammatory mediators in the inflamed colonic tissue. In parallel with the cellular effects of RAME, RAME up-regulated HIF-1α and VEGF in the inflamed colonic tissue. Thus, lipophilic modification of RA improves its ability to inhibit HPH, leading to activation of the HIF-1-VEGF pathway. RAME, a lipophilic RA derivative, may exert anti-colitic effects via activation of the ulcer healing pathway.

Cyclic Adenosine Monophosphate-Mediated Enhancement of Vascular Endothelial Growth Factor Released by Differentiated Human Monocytic Cells: The Role of Protein Kinase A

OBJECTIVE

Our investigation was designed to examine the signaling pathway involved in the enhancement of vascular endothelial growth factor (VEGF) release by β-adrenoceptor agonists.

MATERIALS AND METHODS

Human U937 cells differentiated into macrophages were primed with lipopolysaccharide (LPS) in the absence or presence of β-adrenoceptor agonists and antagonists. The VEGF released and the intracellular cyclic adenosine monophosphate (cAMP) generated were assayed by ELISA. Where necessary, differences between mean values were tested for significance using Student's t test.

RESULTS

Isoprenaline, procaterol and salbutamol concentration-dependently enhanced the release of VEGF induced by LPS in U937 cells. R*,R*-(±)-4-[2-[(2-(3-chlorophenyl)-2-hydroxyethyl)amino]propyl]phenoxyacetic acid (BRL 37344), a selective β3-adrenoceptor agonist, did not enhance VEGF release. Using isoprenaline as an agonist, propranolol, ICI 118551 and atenolol produced a parallel rightward shift of the concentration-response curve with no reduction in the maximum response. The -logKB values were 8.12 ± 0.17, 8.03 ± 0.05 and 7.23 ± 0.05 for propranolol, ICI 118551 and atenolol, respectively, indicating the possible involvement of both β1- and β2-adrenoceptor subtypes. Isoprenaline and prostaglandin E2 concentration-dependently increased cAMP generation in U937 cells. Isoprenaline, db-cAMP and 6-Bnz-cAMP, a protein kinase A (PKA) activator, all enhanced VEGF release induced by LPS, and this effect was abolished by KT 5720 and Rp-cAMPS, which are both selective PKA inhibitors, suggesting that PKA is the downstream effector of cAMP activity. 8-CPT-cAMP, a selective activator of the Epac system, had no effect on VEGF release induced by LPS, indicating that the Epac pathway played no role in the release process.

CONCLUSION

In this study, we established that β1- and β2- but not β3-adrenoceptors mediated cAMP-dependent enhancement of VEGF release induced by LPS in differentiated U937 cells, and that PKA was the downstream effector of cAMP activity.

Mechanisms and models for intestinal fibrosis in IBD

Intestinal fibrosis is a common outcome in IBD leading to significant morbidity that, to date, has no effective medical treatment. Current knowledge regarding potential mechanism(s) of intestinal fibrogenesis and stricture formation is limited, due in large part to the lack of relevant animal models. Although conventional models possess aspects that are advantageous to study specific mechanisms involved in gut fibrosis, most lack the features of a spontaneously occurring process leading to the formation of intestinal fibrotic lesions following mucosal inflammatory events and the ability to investigate the natural course of disease over time. This review aims to discuss established and novel animal models of gut fibrosis, particularly focusing on the advantages and disadvantages of each model system and the insights they bring to our understanding of the mechanisms of fibrogenesis. In fact, recent enhancements to existing models and the expansion of novel animal models of gut fibrosis is opening up multiple avenues for investigation which should stimulate progress in our mechanistic understanding of intestinal fibrogenesis and facilitate the development of effective pharmacotherapy in an area of significant unmet need.

IL-13 orchestrates resolution of chronic intestinal inflammation via phosphorylation of glycogen synthase kinase-3β

Spontaneous amelioration of inflammation (often accompanied by fibrosis) is a well-known, but poorly understood, outcome of many chronic inflammatory processes. We studied this phenomenon in a chronic trinitrobenzene sulfonic acid-induced colitis model, an experimental colitis in mice that we showed to ultimately undergo spontaneous resolution, despite continued trinitrobenzene sulfonic acid stimulation. Analysis of the mechanism of this resolution revealed that it was critically dependent on IL-13 activation of STAT6, followed by phosphorylation (inactivation) of glycogen synthase kinase-3β, at least in part via STAT6 induction of p38 MAPK. Such glycogen synthase kinase-3β inactivation causes changes in CREB and p65 DNA-binding activity that favors decreased proinflammatory IL-17 production and increased anti-inflammatory IL-10 production. Thus, in this case, IL-13 acts as a molecular switch that leads to resolution of inflammation.

Expression of basic fibroblastic growth factor, syndecan 1 and tumour necrosis factor α in resected acute colonic diverticulitis

AIM

Inflammation and fibrosis are present in both colonic diverticulitis and Crohn's disease (CD). The molecular pattern of basic fibroblastic growth factor (bFGF) and syndecan 1 (SD1) expression is altered in stenosing CD, but their expression in resected complicated colonic diverticulitis (ACD) is unknown.

METHOD

The expression of bFGF, SD1 and tumour necrosis factor α (TNF-α) in 20 patients after resection of ACD was compared with 15 patients having a resection for CD. Analysis was conducted using real-time reverse transcriptase polymerase chain reaction in biopsy samples.

RESULTS

Lymphocytic and neutrophil inflammation scores were similar in both groups (P = 0.771 and P = 0.562). TNF-α and bFGF expression was significantly higher in ACD than in CD (P < 0.0001 and P = 0.009). SD1 expression was similar in both groups (P = 0.841).

CONCLUSION

TNF-α and bFGF are significantly overexpressed in ACD with respect to CD, whilst SD1 levels do not differ. The findings confirm that inflammation and its association with altered molecular patterns of mucosal healing may play an important role in the phenotype of the diseases.

Infliximab restores the dysfunctional matrix remodeling protein and growth factor gene expression in patients with inflammatory bowel disease

BACKGROUND

Matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), a disintegrin and metalloprotease with thrombospondin motifs [ADAM(TS)s] and growth factors are involved in inflammation and tissue damage and repair, all occurring in inflammatory bowel disease (IBD). We studied the impact of anti-inflammatory therapy with infliximab on mucosal expression of these tissue remodeling genes in patients with IBD.

METHODS

Mucosal gene expression of 23 MMPs, 4 TIMPs, 50 ADAM(TS)s, and 158 growth factors was investigated in 61 patients with IBD before and after the first infliximab therapy and in 12 controls, with microarrays and quantitative RT-PCR. Protein localization, mucosal gelatinase levels, and net gelatinolytic activity were investigated by immunohistochemistry, zymography analysis, and gelatin degradation assay, respectively.

RESULTS

In patients with active IBD before infliximab versus controls, gene expression of many MMPs, TIMPs, ADAM(TS)s, and growth factors was upregulated, whereas colonic expression of MMP28 and TGFA and ileal expression of ADAMDEC1 and AGT were downregulated. After controlling inflammation with infliximab, most gene dysregulations observed at baseline were restored in responders. Increased ratio of MMP1/TIMP1 expression at baseline in active IBD was restored in responders with colonic mucosal healing. With immunohistochemistry, protein localization differences of MMP1, MMP3, REG1A, and TIMP1 were shown between active IBD and control mucosa. With zymography analysis and gelatin degradation assay, higher gelatinase levels and net gelatinolytic activity were measured before infliximab and levels normalized after infliximab.

CONCLUSIONS

Our data suggest that suppression of inflammation results in the arrest of epithelial damage and subsequent mucosal healing. Therefore, the therapeutic potential of agents targeting MMPs or growth factors as primary therapy seems rather complex.

Novel transcriptional regulation of VEGF in inflammatory processes

Vascular endothelial growth factor (VEGF) is a critical angiogenic factor affecting endothelial cells, inflammatory cells and neuronal cells. In addition to its well-defined positive role in wound healing, pathological roles for VEGF have been described in cancer and inflammatory diseases (i.e. atherosclerosis, rheumatoid arthritis, inflammatory bowel disease and osteoarthritis). Recently, we showed that transcription factors LITAF and STAT6B affected the inflammatory response. This study builds upon our previous results in testing the role of mouse LITAF and STAT6B in the regulation of VEGF-mediated processes. Cells cotransfected with a series of VEGF promoter deletions along with truncated forms of mLITAF and/or mSTAT6B identified a DNA binding site (between −338 and −305 upstream of the transcription site) important in LITAF and/or STAT6B-mediated transcriptional regulation of VEGF. LITAF and STAT6B corresponding protein sites were identified. In addition, siRNA-mediated knockdown of mLITAF and/or mSTAT6B leads to significant reduction in VEGF mRNA levels and inhibits LPS-induced VEGF secretion in mouse RAW 264.7 cells. Furthermore, VEGF treatment of mouse macrophage or endothelial cells induces LITAF/STAT6B nuclear translocation and cell migration. To translate these observations in vivo, VEGF164-soaked matrigel were implanted in whole-body LITAF-deficient animals (TamLITAF^−/−), wild-type mice silenced for STAT6B, and in respective control animals. Vessel formation was found significantly reduced in TamLITAF^−/− as well as in STAT6B-silenced wild-type animals compared with control animals. The present data demonstrate that VEGF regulation by LITAF and/or STAT6B is important in angiogenesis signalling pathways and may be a useful target in the treatment of VEGF diseases.

Role of growth factors in the development of lymphangiogenesis driven by inflammatory bowel disease: a review

Studies on angiogenesis and lymphangiogenesis have gained special relevance in research into factors potentially influencing the pathogenesis and course of inflammatory bowel disease (IBD). The results of the few existing studies on the distribution and density of lymphatic vessels and blood vessels in the context of IBD are controversial. Studies using the specific lymphatic marker podoplanin have revealed a significantly large number of lymphatic vessels in the colonic mucosa of patients with ulcerative colitis and Crohn's disease (compared to patients with normal mucosa), whereas other authors have found no significant differences. However, the role of vascular endothelial growth factor (VEGF) tyrosine-kinase receptor 3 (VEGFR-3) in the onset of IBD has not been analyzed. In recent years new biochemical, molecular, and immunohistochemical studies indicate that several families of growth factors, such as the VEGF family and their receptors, fibroblast growth factor-2, platelet-derived growth factor-BB, hepatocyte growth factor, the angiopoietin system, and integrins may play an important role in the onset of IBD. To date, no comparative studies have analyzed these growth factors and specific lymphatic markers. We examine how growth factors are involved in the development of pathological lymphangiogenesis in patients with IBD and determine whether they play a crucial role in disease exacerbation.

VEGF₁₆₄ isoform specific regulation of T-cell-dependent experimental colitis in mice

BACKGROUND

Inflammatory bowel disease (IBD) consists of Crohn's disease (CD) and ulcerative colitis (UC), two widespread diseases of unknown, multifactorial etiology. Colitis pathology involves a pathological angiogenic response where increases in vascular density participate in colitis histopathology. Vascular endothelial growth factor-A (VEGF-A) is a potent angiogenesis stimulator known to be involved in pathological angiogenesis in several diseases including colitis. However, the pathogenic importance of specific VEGF-A isoforms during T-cell-mediated experimental colitis remains largely unknown.

METHODS

The CD4⁺ CD45RB(high) T-cell transfer model of experimental colitis was used for these studies. The VEGF lac-Z transgenic reporter mouse was used to examine specific cellular sources of VEGF-A production. The VEGF₁₆₄ aptamer (Macugen), adenoviral VEGF₁₆₄, and the VEGF Trap were used to evaluate pathological importance.

RESULTS

VEGF lac-Z reporter mice experiments showed that both infiltrating T cells and local tissue cells produce VEGF-A in the colon during disease. Inhibition of VEGF₁₆₄ using a highly selective RNA aptamer significantly attenuated CD4⁺ CD45RB(high) T-cell-dependent experimental colitis by reducing pathological angiogenesis and inflammatory pathology. Conversely, broad-spectrum VEGF inhibition with VEGF Trap did not attenuate disease, nor did adenoviral VEGF₁₆₄ overexpression significantly alter colitis pathology.

CONCLUSIONS

VEGF₁₆₄ is actively produced by multiple cell types during T-cell-mediated colitis. Importantly, specific inhibition of the VEGF₁₆₄ isoform during T-cell-mediated colitis dose-dependently attenuated disease progression, while broad-scale inhibition of all VEGF-A isoforms was not therapeutically beneficial.

Transforming growth factor-β, a whey protein component, strengthens the intestinal barrier by upregulating claudin-4 in HT-29/B6 cells

TGFβ (isoforms 1-3) has barrier-protective effects in the intestine. The mechanisms involved in regulating tight junction protein expression are poorly understood. The aim of this study was to elucidate TGFβ-dependent protective effects with special attention to promoter regulation of tight junction proteins using the HT-29/B6 cell model. In addition, the effects of whey protein concentrate 1 (WPC1), a natural source of TGFβ in human nutrition, were examined. For this purpose, the claudin-4 promoter was cloned and tested for its activity. It exhibited transactivation in response to TGFβ1, which was intensified when Smad-4 was cotransfected, indicating a Smad-4-dependent regulatory component. Shortening and mutation of the promoter altered and attenuated this effect. WPC1 induced an increase in the claudin-4 protein level and resistance of HT-29/B6 cell monolayers. Anti-TGFβ(1-3) antibodies blocked these whey protein effects, suggesting that a main part of this function was mediated through TGFβ. This effect was observed on intact monolayers as well as when barrier function was impaired by preexposure to IFNγ. In conclusion, TGFβ1 affects claudin-4 gene expression via Smad-4-dependent and -independent transcriptional regulation, resulting in barrier protection, a cytokine effect that is also found in whey protein concentrates used in enteral nutrition.

Role of the endothelium in inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are a complex group of diseases involving alterations in mucosal immunity and gastrointestinal physiology during both initiation and progressive phases of the disease. At the core of these alterations are endothelial cells, whose continual adjustments in structure and function coordinate vascular supply, immune cell emigration, and regulation of the tissue environment. Expansion of the endothelium in IBD (angiogenesis), mediated by inflammatory growth factors, cytokines and chemokines, is a hallmark of active gut disease and is closely related to disease severity. The endothelium in newly formed or inflamed vessels differs from that in normal vessels in the production of and response to inflammatory cytokines, growth factors, and adhesion molecules, altering coagulant capacity, barrier function and blood cell recruitment in injury. This review examines the roles of the endothelium in the initiation and propagation of IBD pathology and distinctive features of the intestinal endothelium contributing to these conditions.

Intestinal growth factors: potential use in the treatment of inflammatory bowel disease and their role in mucosal healing

BACKGROUND

A key feature of inflammatory bowel disease (IBD) is impaired epithelial repair. Human growth factors comprise an array of signaling molecules that lead to ligand-specific signal transduction. Their downstream effects are associated with several cellular functions including epithelial healing in response to injury. Several studies have described specific growth factor deficiencies in patients with IBD, implicating their role in disease pathophysiology. The aim of this review was to describe currently known enterocyte-targeted growth factors, their mechanisms of action, and their potential therapeutic utility.

METHODS

The National Library of Medicine (http://www.pubmed.gov) and meeting abstracts were searched using the following terms: growth factor, intestine, colon, inflammatory bowel disease, Crohn's disease, ulcerative colitis, colitis, animal model, transforming growth factor, bone morphogenetic protein, activins, growth hormone, fibroblast growth factor, epidermal growth factor (EGF), keratinocyte growth factor (KGF), glucagon-like peptide II, granulocyte macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), vascular endothelial growth factor (VEGF) inhibitors, and trefoil factors.

RESULTS

Several growth factors are therapeutic candidates in IBD. Growth hormone, KGF, EGF, teduglutide, GM-CSF/G-CSF have entered early clinical trials, whereas others are currently in preclinical evaluation.

CONCLUSIONS

There are several growth factors responsible for epithelial repair. Preliminary studies using recombinant growth factors seem promising in IBD preclinical and clinical trials.

Downregulation of serum epidermal growth factor in patients with inflammatory bowel disease. Is there a link with mucosal damage?

BACKGROUND

Epidermal growth factor (EGF) is a multipotent peptide which contributes to epithelial development, inhibition of gastric acid secretion, acceleration of wound healing, and promotion of angiogenesis. The aim of this study is to evaluate serum EGF concentrations in inflammatory bowel disease (IBD) patients, with regard to disease and patients' characteristics.

METHODS

EGF determination was performed by a commercially available enzyme-linked immunosorbent assay. Fifty-two patients with ulcerative colitis (UC), 59 with Crohn's disease (CD), and 55 healthy controls (HC) were included in the study.

RESULTS

Mean ( ± SEM) serum EGF levels were 217.2 ( ± 30.40) pg/mL in UC patients, 324.6 ( ± 37.29) pg/mL in CD patients, and 453.1 ( ± 39.44) pg/mL in HC. Serum EGF levels were significantly lower in UC and CD patients compared to HC (P < 0.0001 and P = 0.0199, respectively). Lower serum EGF levels were observed in UC compared to CD patients (P = 0.0277). Extent of the disease was found to affect serum EGF levels in UC, demonstrating significant reduction in patients with left-sided colitis and pancolitis in comparison with those with proctitis (P = 0.0190 and P = 0.0024, respectively). EGF concentration was not influenced by other characteristics of patients and disease.

CONCLUSIONS

Significantly, lower levels of serum EGF are observed in IBD patients compared to HC, while disease extent plays a key role in regulation of serum EGF in UC. Downregulation of serum EGF may be correlated with different patterns of bowel inflammation, epithelial development, and wound healing in IBD.

Hepatocyte growth factor and keratinocyte growth factor enhance IL-1-induced IL-8 secretion through different mechanisms in Caco-2 epithelial cells

A variety of cytokines have been detected in inflamed intestinal mucosal tissues, including the pro-inflammatory cytokine, interleukin-1 (IL-1), along with growth factors involved in wound healing processes such as proliferation and cell migration. However, little is known about how IL-1 and growth factors interact with intestinal epithelial cells to regulate the production of inflammatory cytokines such as interleukin-8 (IL-8). Previously, we have shown that hepatocyte growth factor (HGF) could significantly enhance IL-1-stimulated IL-8 secretion by the Caco-2 colonic epithelial cell line, yet HGF, by itself, did not stimulate IL-8 secretion. In this report, a second growth factor, keratinocyte growth factor (KGF), was also found to significantly enhance IL-1-induced IL-8 secretion by Caco-2 cells, yet KGF, by itself, also had no effect. Simultaneous addition of both IL-1 and KGF was also required for the enhancing effect. Treatment of the Caco-2 cells with wortmannin or triciribine suppressed the enhancing effect of HGF, suggesting that the effect was mediated by signaling through phosphatidylinositol-3-kinase (PI3K) and the kinase AKT. The enhancing effect of KGF was not affected by wortmannin, but was suppressed by triciribine, suggesting that the effect of KGF was through a PI3K-independent activation of AKT. These results suggest that the growth factors HGF and KGF may play a role in enhancing IL-1-stimulated production of IL-8 by epithelial cells during mucosal inflammations. However, the mechanism by which the growth factors enhance the IL-1 response may be through different initial signaling pathways.

Toll-like receptor 4 differentially regulates epidermal growth factor-related growth factors in response to intestinal mucosal injury

Epiregulin (EPI) and amphiregulin (AR) are epidermal growth factor receptor (EGFR) ligands implicated in mucosal repair and tumorigenesis. We have shown that Toll-like receptor 4 (TLR4) induces intestinal epithelial cell (IEC) proliferation by activating EGFR through AR expression. We examined whether TLR4 differentially regulates expression of EGFR ligands in response to mucosal injury. The human IEC line SW480 was examined expression of EGFR ligands, EGFR phosphorylation, and proliferation in response to lipopolysaccharide (LPS). Small-interfering RNA (siRNA) was used to block TLR4. Neutralizing antibodies to EGFR ligands were used to examine inhibition of LPS-dependent EGFR activation. Acute colitis and recovery were examined in the mice given 2.5% dextran sodium sulfate (DSS). Colonic secretion of EPI and AR was analyzed by enzyme-linked immunosorbent assay. LPS selectively induces EPI and AR but not other EGFR ligands. LPS induced early EPI mRNA expression between 30 min and 24 h. The neutralizing antibodies to EPI and AR prevented activation of EGFR by LPS. LPS induces IEC proliferation (200%, P=0.01) in 24 h but blocking EPI and AR significantly decreased proliferation. In vivo, mucosal EPI and AR expression are significantly decreased in TLR4(-/-) mice (P=0.02) compared to wild-type mice during acute colitis. EPI and AR exhibit different kinetics in response to mucosal damage: EPI expression is upregulated acutely at day 7 of DSS, but falls during recovery at day 14. By contrast, a sustained upregulation of AR expression is seen during mucosal injury and repair. We show that TLR4 regulates EPI and AR expression and that both these EGFR ligands are necessary for optimal proliferation of IEC. The diverse kinetics of EPI and AR expression suggest that they function in distinct roles with respect to acute injury vs repair. Our results highlight the role of bacterial sensing for IEC homeostasis and may lead to targeted therapy for mucosal healing and prevention of tumorigenesis.

Assessment of Growth Disturbance in Japanese Children with IBD

In Japan, there is as yet no report on growth retardation in children with IBD. We therefore investigated the cause of growth retardation in Japanese children with IBD. We investigated the height, body weight, serum levels of albumin, IGF-I, CRP, and cytokines, and the amount of corticosteroid administered in children with Crohn's disease (CD, n = 15) and ulcerative colitis (UC, n = 18). Our results suggest that growth retardation is already present before the initial visit in children with CD, and chronic inflammation may be responsible this growth disturbance. Moreover, the amount of PSL used may contribute to growth retardation by decreasing the serum levels of IGF-I in children with IBD.

Current directions of biologic therapies in inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory bowel diseases which can be difficult to control with conventional therapies. A greater understanding of their pathophysiology has led to new therapies that target specific molecules of the inflammatory cascade. Three anti-tumor necrosis factor (TNF) monoclonal antibodies have been developed. Infliximab and adalimumab can induce clinical response and sustained remission in CD. Infliximab is also effective in UC. Certolizumab pegol gives good short-term results but long-term efficacy has yet to be determined in other clinical trials. Therapies that target leucocyte trafficking (anti-integrins) have also been developed and are associated with good clinical response in CD. Natalizumab (anti-α4 integrin antibody) is associated with important side effects and is not used anymore in gastroenterology in Europe but is still used in the USA. Vedolizumab (MLN0002), an anti-α4β7 integrin antibody, has a good efficacy and safety profile. Monoclonal antibodies targeting other cytokines are also under development. For example, ustekinumab (CNTO 1275) inhibits interleukins 12 and 23. It is associated with a good clinical response in CD.

Insulin-like growth factor 1-coated sutures improve anastomotic healing in an experimental model of colitis

BACKGROUND

: Exogenously applied insulin-like growth factor (rhIGF-1) may improve normal intestinal healing. This study examined the effect of rhIGF-1-coated sutures on anastomotic healing in experimental colitis.

METHODS

: Acute colitis was induced in rats by dextran sodium sulphate (DSS). Inflammation was assessed by clinical Disease Activity Index (DAI), myeloperoxidase (MPO) measurement and histological examination. A distal colonic anastomosis was performed using sutures coated with rhIGF-1 dissolved in poly(D,L-lactide) (PDLLA) under general anaesthetic. Anastomotic healing was evaluated histologically, and by hydroxyproline measurement and bursting parameters after 1, 3 and 7 days, and compared with healthy, DSS and DSS + PDLLA controls.

RESULTS

: DAI, MPO and histological inflammation scores were significantly increased in all animals treated with DSS. Bursting occurred less often within the anastomotic line on day 3 in the IGF group than in DSS controls (three versus eight of ten). On day 7, the IGF group had significantly increased histological healing scores (mean(s.e.m.) 12.5(0.7) versus 9.2(0.8) (P < 0.050)) and hydroxyproline content (4.6(0.3) versus 3.6(0.1) mg/g tissue; P < 0.050) compared with DSS controls.

CONCLUSION

: IGF-1-coated sutures improve important aspects of anastomotic healing in rats with experimental colitis.

[Multifactorial etiology and pathogenic factors in inflammatory bowel disease]

All the currently available evidence suggests that the two types of inflammatory bowel disease (IBD), Crohn's disease (CD) and ulcerative colitis (UC), involve a conflict between the immune system of the intestinal mucosa and intraluminal antigens, mainly the intestinal microflora, which are normally tolerated by the immune system. This conflict is modulated by numerous environmental factors and a clear polygenetic predisposition. The present article reviews the behavior of all the etiologic circumstances (microbial, genetic and environmental) and subsequently analyzes the possible pathogenic factors in which the etiologies can be found, namely: dysfunction of the intestinal epithelium, innate immune system alterations, and distortion of the cellular and humoral arms of the acquired immune system. The role of tissue ischemia in CD and expression of "extraintestinal inflammatory metastases", both in CD and UC, are briefly discussed. Finally, the view that IBD may be a spectrum of pathological processes provoked by distinct etiopathogenic factors and the possible biological significance of the growing incidence of this disease in the western world, coinciding with the decline in infectious diseases in this geographical area, are discussed.

Growth factors as treatment for inflammatory bowel disease: a concise review of the evidence toward their potential clinical utility

In the process of inflammation and repair of the intestinal mucosa in inflammatory bowel disease (IBD), there occurs a complex and an unknown interplay of innate and adaptive immune mechanisms. This interaction of factors may explain why IBD is characterized by a relapsing and remitting clinical course. Different components of innate immunity, hormones and interleukins in IBD have been suggested to be impaired. The growth hormone, epidermal growth factor, keratinocyte growth factor and colony-stimulating factors have emerged as potential tools for the modulation of intestinal inflammation and repair. Despite promising results of initial studies, the evidence that justify treatment of patients in clinical practice is not enough as some of the trials are nonrandomized or included a small number of patients. In this concise review, we provide a summary of the most recent and relevant evidence regarding the potential therapeutic effects of growth factors in IBD.

TGF-beta and fibrosis in different organs - molecular pathway imprints

The action of transforming-growth-factor (TGF)-beta following inflammatory responses is characterized by increased production of extracellular matrix (ECM) components, as well as mesenchymal cell proliferation, migration, and accumulation. Thus, TGF-beta is important for the induction of fibrosis often associated with chronic phases of inflammatory diseases. This common feature of TGF-related pathologies is observed in many different organs. Therefore, in addition to the description of the common TGF-beta-pathway, this review focuses on TGF-beta-related pathogenetic effects in different pathologies/organs, i. e., arthritis, diabetic nephropathy, colitis/Crohn's disease, radiation-induced fibrosis, and myocarditis (including their similarities and dissimilarities). However, TGF-beta exhibits both exacerbating and ameliorating features, depending on the phase of disease and the site of action. Due to its central role in severe fibrotic diseases, TGF-beta nevertheless remains an attractive therapeutic target, if targeted locally and during the fibrotic phase of disease.

Carcinogenesis in IBD: potential targets for the prevention of colorectal cancer

In patients with IBD, chronic colonic inflammation increases the risk of colorectal cancer, perhaps because inflammation predisposes these tissues to genomic instability. Carcinogenesis in the inflamed colon seems to follow a different sequence of genetic alterations than that observed in sporadic cancers in the uninflamed colon. In this Review, we focus on the genetic alterations in colitis-associated colorectal cancer that contribute to the acquisition of the essential hallmarks of cancer, and on how those alterations differ from sporadic colorectal cancers. Our intent is to provide a conceptual basis for categorizing carcinogenetic molecular abnormalities in IBD, and for understanding how cancer-preventive therapies might target reversal of acquired abnormalities in specific biochemical pathways.

Enhanced expression of transcription factor GATA-4 in inflammatory bowel disease and its possible regulation by TGF-beta1

BACKGROUND

Transforming growth factor beta 1 (TGF-beta1) promotes epithelial healing in inflammatory bowel disease. We hypothesized that GATA-4, a transcription factor cooperating with TGF-beta signaling pathway, is upregulated by TGF-beta1 in the inflamed intestinal epithelium.

METHODS

Normal and inflamed intestinal samples were subjected to immunohistochemistry for GATA-4/6 and the TGF-beta signaling pathway components Smad2/3/4. Proliferation and apoptosis were analyzed using Ki-67 and in situ DNA 3'-end labeling assays and Bax and Bcl-2 immunohistochemistry. Furthermore, GATA-4 was assessed in intestinal Caco-2 cells stimulated with TGF-beta1, or interleukin-6 and tumor necrosis factor alpha.

RESULTS

GATA-4 was detected in only 20% of normal intestinal samples, but was upregulated in corresponding inflamed regions. GATA-6 expression remained unchanged during inflammation. TGF-beta1 and Smad3/4, but not Smad2, were expressed concomitantly with GATA-4 in inflamed bowel mucosa. In intestinal Caco-2 cells, TGF-beta1 upregulated GATA-4 and Smad2/3/4, whereas treatment with control cytokines had no effect. Inflammation was associated with increased epithelial cell apoptosis and the enhancement of Bcl-2, but not Bax.

CONCLUSIONS

We surmise GATA-4 expression is upregulated in inflamed intestine correlating with the activation of TGF-beta signaling pathway. We speculate that TGF-beta1 drives GATA-4 expression during intestinal inflammation, these two components cooperating to promote epithelial healing.

Cytokines mediating the induction of chronic colitis and colitis-associated fibrosis

To investigate the immunopathogenesis of inflammation-associated fibrosis we analyzed the chronic colitis and late-developing fibrosis occurring in BALB/c mice administered weekly doses of intrarectal trinitrobenzene sulfonic acid (TNBS). We showed first in this model that an initial T helper type 1 response involving interleukin (IL)-12p70 and interferon-gamma subsides after 3 weeks to be supplanted by an IL-23/IL-25 response beginning after 4-5 weeks. This evolution is followed by gradually increasing production of IL-17 and cytokines ordinarily seen in a T helper type 2 response, particularly IL-13, which reaches a plateau at 8-9 weeks. We then show that IL-13 production results in the induction of an IL-13 receptor formerly thought to function only as a decoy receptor, IL-13Ralpha(2), and this receptor is critical to the production of tumor growth factor (TGF)-beta(1) and the onset of fibrosis. Thus, if IL-13 signaling through this receptor is blocked by administration of soluble IL-13Ralpha(2)-Fc, or by administration of IL-13Ralpha(2)-specific siRNA, TGF-beta(1) is not produced and fibrosis does not occur. These studies show that in chronic TNBS colitis, fibrosis is dependent on the development of an IL-13 response that acts through a novel cell-surface-expressed IL-13 receptor to induce TGF-beta(1).

Novel regulation of vascular endothelial growth factor-A (VEGF-A) by transforming growth factor (beta)1: requirement for Smads, (beta)-CATENIN, AND GSK3(beta)

Vascular endothelial growth factor (VEGF) is a vital angiogenic effector, regulating key angiogenic processes. Vascular development relies on numerous signaling pathways, of which those induced by transforming growth factor-beta (TGFbeta) are critical. The Wnt/beta-catenin signaling pathway is emerging as necessary for vascular development. Although VEGF, TGFbeta, and Wnt signal transductions are well studied individually, it has not been demonstrated previously that all three can interact or be dependent on each other. We show that regulation of VEGF by TGFbeta(1), in human pulmonary artery smooth muscle cells (PASMCs), depends on a direct interaction between TGFbeta signaling proteins, Smads, and members of the Wnt/beta-catenin signaling family. VEGF promoter reporter constructs identified a region of the VEGF promoter containing two T cell factor (TCF)-binding sites as necessary for TGFbeta(1)-induced VEGF transcription. Mutation of TCF sites and expression of dominant negative TCF4 abolished TGFbeta(1)-induced VEGF promoter activity. Studies in Smad2 and Smad3 knock-out mouse embryonic fibroblasts demonstrated that one or both are required for VEGF regulation by TGFbeta(1), with transfection of dominant negative Smad2 or Smad3 into PASMCs confirming this. Chromatin immunoprecipitation assays showed in cell interactions of Smad2 and Smad3 with TCF4 and beta-catenin at the VEGF promoter, whereas co-immunoprecipitation showed a direct physical interaction between Smad2 and beta-catenin in the nucleus of PASMCs. Finally, we demonstrate that TGFbeta(1) regulates TCF by modifying beta-catenin phosphorylation via regulation of glycogen synthase kinase 3beta. These results provide new insight into the molecular regulation of VEGF by two interacting pathways necessary for vascular development, maintenance, and disease.

Review article: new drug formulations, chemical entities and therapeutic approaches for the management of ulcerative colitis

BACKGROUND

Treatment options for ulcerative colitis (UC) are expanding with the development of novel drug formulations and dosing regimens and new chemical entities. Although the goals of medical therapy for UC remain unchanged, that is to induce and to maintain remission, focus has also centred on improving patient compliance, modifying the natural course of disease and healing the mucosa.

AIM

To examine novel formulations, new chemical entities and novel therapeutic approaches to the management of UC.

METHODS

Searches for all studies related to UC treatment in Medline and abstracts from major national and international meetings published in the last 10 years.

RESULTS

5-Aminosalicylic acids (5-ASA) remain the standard first-line treatment for patients with mild to moderately active UC. New formulations with altered delivery, and new dosing regimens have demonstrated possible improvements in efficacy compared with historically available preparations and dosing patterns. Once-daily dosing, micropellet formulations,and high-dose tablets offer enhanced efficacy and improved compliance. 5-ASA is now recognized as a ligand for peroxisome proliferator activated receptor-gamma (PPAR-gamma) and it has a role as a chemo-preventive agent in long-standing UC. New colonic release corticosteroid formulations help to limit systemic toxicity; turmeric, tacrolimus and infliximab have shown promising results. New anti-inflammatory targeted therapies include an anti-CD3 antibody, selective integrin blockers, anti-IL-2 antibody and PPAR-gamma agonists.

CONCLUSION

The evolution of novel oral 5-ASA formulations and dosage regimens,and recent development of new molecules have expanded the therapeutic armamentarium of UC.

Biological agents for ulcerative colitis: hypes and hopes

Ulcerative colitis (UC) is an idiopathic chronic inflammatory disease of the colonic mucosa. Over the last decade, the increasing knowledge on the pathogenic mechanisms underlying intestinal inflammation has led to the development of a number of biological agents, mainly addressed to molecules and/or pathways demonstrated to have a pathogenic role in UC. In UC, clinical course and therapeutic decisions mainly depend on disease activity and extent. While therapeutic approach to mild-to-moderate UC by using aminosalicylates and corticosteroids has been well established, treatment of severe UC is far from being satisfactory. A severe attack of UC remains a challenge to be managed jointly by gastroenterology, surgery, and intensive care units. However, the recent introduction of biological therapies has led to promising changes in the management of UC patients. Aim of this paper is to review the recent advances and future perspectives for the use of biological agents in UC.

Angiogenesis in inflammatory bowel disease

Both ulcerative colitis and Crohn's disease, the two major forms of inflammatory bowel diseases, are recognized, at the moment, as perplexing and challenging clinical entities, in which several molecules and cell types are implicated. Recent molecular evidence proposes the intestinal microvascular remodelling or angiogenesis, as a phenomenon implicated in the pathogenesis of these chronic inflammatory disorders, together with other proposed theories involved in the pathogenesis of inflammatory bowel diseases, such as genetic, microbacterial and immune factors. Intestinal damage is followed by a physiological angiogenesis, but the abnormal expression of pro- and anti-angiogenic molecules and the changes of vascular cell types could reflect a pathological vascular remodelling. Thus, the inflammation may be favoured and maintained by a pathological angiogenesis. A better understanding of the angiogenic process may facilitate the design of more effective therapies for chronic intestinal inflammation.

Epithelial restitution and wound healing in inflammatory bowel disease

Inflammatory bowel disease is characterized by a chronic inflammation of the intestinal mucosa. The mucosal epithelium of the alimentary tract constitutes a key element of the mucosal barrier to a broad spectrum of deleterious substances present within the intestinal lumen including bacterial microorganisms, various dietary factors, gastrointestinal secretory products and drugs. In addition, this mucosal barrier can be disturbed in the course of various intestinal disorders including inflammatory bowel diseases. Fortunately, the integrity of the gastrointestinal surface epithelium is rapidly reestablished even after extensive destruction. Rapid resealing of the epithelial barrier following injuries is accomplished by a process termed epithelial restitution, followed by more delayed mechanisms of epithelial wound healing including increased epithelial cell proliferation and epithelial cell differentiation. Restitution of the intestinal surface epithelium is modulated by a range of highly divergent factors among them a broad spectrum of structurally distinct regulatory peptides, variously described as growth factors or cytokines. Several regulatory peptide factors act from the basolateral site of the epithelial surface and enhance epithelial cell restitution through TGF-β-dependent pathways. In contrast, members of the trefoil factor family (TFF peptides) appear to stimulate epithelial restitution in conjunction with mucin glycoproteins through a TGF-β-independent mechanism from the apical site of the intestinal epithelium. In addition, a number of other peptide molecules like extracellular matrix factors and blood clotting factors and also non-peptide molecules including phospholipids, short-chain fatty acids (SCFA), adenine nucleotides, trace elements and pharmacological agents modulate intestinal epithelial repair mechanisms. Repeated damage and injury of the intestinal surface are key features of various intestinal disorders including inflammatory bowel diseases and require constant repair of the epithelium. Enhancement of intestinal repair mechanisms by regulatory peptides or other modulatory factors may provide future approaches for the treatment of diseases that are characterized by injuries of the epithelial surface.

Insights from advances in research of chemically induced experimental models of human inflammatory bowel disease

Inflammatory bowel disease (IBD), the most important being Crohn's disease and ulcerative colitis, results from chronic dysregulation of the mucosal immune system in the gastrointestinal tract. Although the pathogenesis of IBD remains unclear, it is widely accepted that genetic, environmental, and immunological factors are involved. Recent studies suggest that intestinal epithelial defenses are important to prevent inflammation by protecting against microbial pathogens and oxidative stresses. To investigate the etiology of IBD, animal models of experimental colitis have been developed and are frequently used to evaluate new anti-inflammatory treatments for IBD. Several models of experimental colitis that demonstrate various pathophysiological aspects of the human disease have been described. In this manuscript, we review the characteristic features of IBD through a discussion of the various chemically induced experimental models of colitis (e.g., dextran sodium sulfate-, 2,4,6-trinitrobenzene sulfonic acid-, oxazolone-, acetic acid-, and indomethacin-induced models). We also summarize some regulatory and pathogenic factors demonstrated by these models that can, hopefully, be exploited to develop future therapeutic strategies against IBD.

Alleviation of experimental ulcerative colitis with the synthetic peptide, F2A4-K-NS (Fibratide)

Recombinant fibroblast growth factors (FGFs) maintain the integrity of the gut epithelium and reduce mucosal injury in experimental inflammatory bowel disease (IBD). Chemically synthesized FGF mimetics could potentially extend the utility of FGFs by tailoring them for optimal bioactivity and oral administration, for example. Here, F2A4-K-NS (Fibratide), a synthetic FGF mimetic peptide, alleviated dextran sulfate sodium (DSS)-induced ulcerative colitis in mice when delivered systemically and, to a lesser extent, orally. Intraperitoneal injection of Fibratide (1 or 5 mg/kg/day) ameliorated DSS-induced ulcerative colitis, resulting in reduced weight loss, decreased colon wall thickening, and increased colon length. Fibratide also improved epithelial integrity by reducing histological-detectable crypt damage and inflammation. Orally administered Fibratide (1 mg/kg/day) was also effective in ameliorating symptoms with effects generally similar to those of intraperitoneal injection. In vitro studies were conducted to help clarify how Fibratide might act in vivo. Fibratide exhibited a modest enhancement of epithelial cell proliferation. On the other hand, Fibratide doubled the rate of epithelial cells migration and restitution in a cell culture model of wound repair. Collectively, the results indicate that Fibratide reduced the severity of experimental ulcerative colitis and may be potentially useful in the treatment of IBD.

Pathogenic angiogenesis in IBD and experimental colitis: new ideas and therapeutic avenues

Angiogenesis is now understood to play a major role in the pathology of chronic inflammatory diseases and is indicated to exacerbate disease pathology. Recent evidence shows that angiogenesis is crucial during inflammatory bowel disease (IBD) and in experimental models of colitis. Examination of the relationship between angiogenesis and inflammation in experimental colitis shows that initiating factors for these responses simultaneously increase as disease progresses and correlate in magnitude. Recent studies show that inhibition of the inflammatory response attenuates angiogenesis to a similar degree and, importantly, that inhibition of angiogenesis does the same to inflammation. Recent data provide evidence that differential regulation of the angiogenic mediators involved in IBD-associated chronic inflammation is the root of this pathological angiogenesis. Many factors are involved in this phenomenon, including growth factors/cytokines, chemokines, adhesion molecules, integrins, matrix-associated molecules, and signaling targets. These factors are produced by various vascular, inflammatory, and immune cell types that are involved in IBD pathology. Moreover, recent studies provide evidence that antiangiogenic therapy is a novel and effective approach for IBD treatment. Here we review the role of pathological angiogenesis during IBD and experimental colitis and discuss the therapeutic avenues this recent knowledge has revealed.

Induction of IL-13 triggers TGF-beta1-dependent tissue fibrosis in chronic 2,4,6-trinitrobenzene sulfonic acid colitis

To investigate the immunopathogenesis of inflammation-associated fibrosis, we analyzed the chronic colitis and late-developing fibrosis occurring in BALB/c mice administered weekly doses of intrarectal 2,4,6-trinitrobenzene sulfonic acid. We showed first in this model that an initial Th1 response involving IL-12p70 and IFN-gamma subsides after 3 wk to be supplanted by an IL-23/IL-25 response beginning after 4-5 wk. This evolution is followed by gradually increasing production of IL-17 and cytokines ordinarily seen in a Th2 response, particularly IL-13, which reaches a plateau at 8-9 wk. In vitro stimulation studies suggest that this IL-13 production is dependent on IL-23 and IL-25, but not on IL-12p70. We then show that IL-13 production results in the induction of an IL-13R formerly thought to function only as a decoy receptor, IL-13Ralpha(2), and this receptor is critical to the production of TGF-beta(1) and the onset of fibrosis. Thus, if IL-13 signaling through this receptor is blocked by administration of soluble IL-13Ralpha(2)-Fc, or by administration of IL-13Ralpha(2)-specific small interfering RNA, TGF-beta(1) is not produced and fibrosis does not occur. These studies show that in chronic 2,4,6-trinitrobenzene sulfonic acid colitis, fibrosis is dependent on the development of an IL-13 response that acts through a novel cell surface-expressed IL-13R to induce TGF-beta(1). A similar mechanism may obtain in certain forms of human inflammatory bowel disease.

Blockade of TGF-beta accelerates mucosal destruction through epithelial cell apoptosis

To clarify the protective role of transforming growth factor (TGF)-beta for the intestinal epithelial injury in vivo, the effect of antibodies against TGF-beta on epithelial destruction and apoptosis was assessed in dextran sulfate sodium (DSS)-induced colitis by histological analysis of colonic sections, account of apoptotic epithelial cells. To evaluate the pathways of epithelial apoptosis, we analyzed the activities of caspases, the level of Fas and cellular FLICE-inhibitory protein (cFLIP) expression in epithelial cells. Apoptotic epithelial cells were increased prior to the onset of ulceration in DSS-induced colitis, and the neutralization of TGF-beta exacerbated epithelial apoptosis and histological damage score. The up-regulation of caspase-8 activity and Fas expression and reduced cFLIP expression were observed in intestinal epithelial cells from anti-TGF-beta antibody-treated mice. The present study revealed that suppression of TGF-beta deteriorated epithelial apoptosis, and the increase of apoptotic epithelial cells may amplify the inflammation in gut mucosa.