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The endocannabinoid system of the gastrointestinal tract is involved in the control of intestinal barrier function. Whether the cannabinoid 1 (CB

The endocannabinoid system of the gastrointestinal tract regulates homeostasis by acting as brake on motility and secretion. Here we show that when exposed to a high fat diet, intestinal permeability is increased and activation of the CB1 receptor on the intestinal epithelium restores barrier function. This work further highlights the role of the endocannabinoid system in regulating intestinal homeostasis when it is perturbed.

Mucosal and histological healing have become the gold standards for assessing the efficacy of therapy in patients living with inflammatory bowel diseases (IBD). Despite these being the accepted goals in therapy, the mechanisms that underlie the healing of the mucosa after an inflammatory insult are not well understood, and many patients fail to meet this therapeutic endpoint. Here we review the emerging evidence that mediators (e.g., prostaglandins, cytokines, proteases, reactive oxygen, and nitrogen species) and innate immune cells (e.g., neutrophils and monocytes/macrophages), that are involved in the initiation of the inflammatory response, are also key players in the mechanisms underlying mucosal healing to resolve chronic inflammation in the colon. The dual function mediators comprise an inflammation/repair program that returns damaged tissue to homeostasis. Understanding details of the dual mechanisms of these mediators and cells may provide the basis for the development of drugs that can help to stimulate epithelial repair in patients affected by IBD.

The small intestine regulates barrier function to absorb nutrients while avoiding the entry of potentially harmful substances or bacteria. Barrier function is dynamically regulated in part by the enteric nervous system (ENS). The role of the ENS in regulating barrier function in response to luminal nutrients is not well understood. We hypothesize that the ENS regulates intestinal permeability and ion flux in the small intestine in response to luminal nutrients. Segments of jejunum and ileum from mice were mounted in Ussing chambers. Transepithelial electrical resistance (TER), short-circuit current ( Isc), and permeability to 4-kDa FITC-dextran (FD4) were recorded after mucosal stimulation with either glucose, fructose, glutamine (10 mM), or 5% Intralipid. Mucosal lipopolysaccharide (1 mg/mL) was also studied. Enteric neurons were inhibited with tetrodotoxin (TTX; 0.5 μM) or activated with veratridine (10 μM). Enteric glia were inhibited with the connexin‐43 blocker Gap26 (20 μM). Glucose, glutamine, Intralipid, and veratridine acutely modified Isc in the jejunum and ileum, but the effect of nutrients on Isc was insensitive to TTX. TTX, Gap26, and veratridine treatment did not affect baseline TER or permeability. Intralipid acutely decreased permeability to FD4, while LPS increased it. TTX pretreatment abolished the effect of Intralipid and exacerbated the LPS‐induced increase in permeability. Luminal nutrients and enteric nerve activity both affect ion flux in the mouse small intestine acutely but independently of each other. Neither neuronal nor glial activity is required for the maintenance of baseline intestinal permeability; however, neuronal activity is essential for the acute regulation of intestinal permeability in response to luminal lipids and lipopolysaccharide. NEW & NOTEWORTHY Luminal nutrients and enteric nerve activity both affect ion transport in the mouse small intestine acutely, but independently of each other. Activation or inhibition of the enteric neurons does not affect intestinal permeability, but enteric neural activity is essential for the acute regulation of intestinal permeability in response to luminal lipids and lipopolysaccharide. The enteric nervous system regulates epithelial homeostasis in the small intestine in a time-dependent, region- and stimulus-specific manner.

Background and purpose Dietary fibre comprises a complex group of polysaccharides that are indigestible but are fermented by gut microbiota, promoting beneficial effects to the intestinal mucosa indirectly through the production of short chain fatty acids. We found that a polysaccharide, rhamnogalacturonan (RGal), from the plant Acmella oleracea, has direct effects on intestinal epithelial barrier function. Our objective was to determine the mechanism whereby RGal enhances epithelial barrier function. Experimental approach Monolayers of colonic epithelial cell lines (Caco-2, T84) and of human primary cells from organoids were mounted in Ussing chambers to assess barrier function. The cellular mechanism of RGal effects on barrier function was determined using inhibitors of TLR-4 and PKC isoforms. Key results Apically applied RGal (1000 μg/ml) significantly enhanced barrier function as shown by increased transepithelial electrical resistance (TER) and reduced fluorescein isothiocyanate (FITC)-dextran flux in Caco-2, T84 and human primary cell monolayers, and accelerated tight junction reassembly in Caco-2 cells in a calcium switch assay. RGal also reversed the barrier-damaging effects of inflammatory cytokines on FITC-dextran flux and preserved the tight junction distribution of occludin. RGal activated TLR4 in TLR4-expressing HEK reporter cells, an effect that was significantly inhibited by the TLR4 inhibitor, C34. The effect of RGal was also dependent on PKC, specifically the isoforms PKCd and PKCζ. Conclusion and implications RGal enhances intestinal epithelial barrier function through activation of TLR4 and PKC signaling pathways. Elucidation of RGal mechanisms of action could lead to new, dietary approaches to enhance mucosal healing in inflammatory bowel diseases.

The intestinal barrier function relies on the presence of a single layer of epithelial cells. Barrier dysfunction is associated with the inflammatory bowel diseases (IBD). Understanding the mechanisms involved in intestinal wound healing in order to sustain the barrier function has a great therapeutic potential. Activation of protease-activated receptor-2 (PAR2) induces COX-2 expression in intestinal epithelial cells via EGFR transactivation. COX-2 is well known for its protective effects in the gastrointestinal tract. Therefore, we hypothesized that PAR-2 activation induces a wound healing response in intestinal epithelial cells through COX-2-derived lipid mediators and EGFR transactivation. Immunofluorescence and calcium assay were used to characterize CMT-93 mouse colonic epithelial cell line for PAR2 expression and its activity, respectively. Treatment with PAR2 activating peptide 2-furoyl-LIGRLO-NH(2) (2fLI), but not by its inactive reverse-sequence peptide (2fO) enhanced wound closure in scratch wounded monolayers. The EGFR tyrosine kinase inhibitor (PD153035), broad-spectrum matrix metalloproteinase inhibitor (GM6001) and Src tyrosine kinase inhibitor (PP2) inhibited PAR2-induced wound healing. However, PAR2 activation did not induce COX-2 expression in CMT-93 cells and inhibition of COX-2 by COX-2 selective inhibitor (NS-398) did not alter PAR2-induced wound healing. In conclusion, PAR2 activation drives wound healing in CMT-93 cells via EGFR transactivation. Matrix metalloproteinases and Src tyrosine kinase activity may involve in EGFR transactivation and PAR2-induced wound healing is independent of COX-2 activity. These findings provide a mechanism whereby PAR2 can participate in the resolution of intestinal wounds in gastrointestinal inflammatory diseases.

Dysregulated protease activity is often implicated in the initiation of inflammation and immune cell recruitment in gastrointestinal inflammatory diseases. Using N-terminomics/TAILS (terminal amine isotopic labeling of substrates), we compared proteases, along with their substrates and inhibitors, between colonic mucosal biopsies of healthy patients and those with ulcerative colitis (UC). Among the 1642 N-termini enriched using TAILS, increased endogenous processing of proteins was identified in UC compared to healthy patients. Changes in the reactome pathways for proteins associated with metabolism, adherens junction proteins (E-cadherin, liver-intestinal cadherin, catenin alpha-1, and catenin delta-1), and neutrophil degranulation were identified between the two groups. Increased neutrophil infiltration and distinct proteases observed in ulcerative colitis may result in extensive break down, altered processing, or increased remodeling of adherens junctions and other cellular functions. Analysis of the preferred proteolytic cleavage sites indicated that the majority of proteolytic activity and processing comes from host proteases, but that key microbial proteases may also play a role in maintaining homeostasis. Thus, the identification of distinct proteases and processing of their substrates improves the understanding of dysregulated proteolysis in normal intestinal physiology and ulcerative colitis.

Summary Many patients with visceral inflammation develop pain and psychiatric comorbidities such as major depressive disorder, worsening the quality of life and increasing the risk of suicide. Here we show that neuroimmune activation in mice with dextran sodium sulfate-induced colitis is accompanied by the development of pain and depressive behaviors. Importantly, treatment with the flavonoid luteolin prevented both neuroimmune responses and behavioral abnormalities, suggesting a new potential therapeutic approach for patients with inflammatory bowel diseases., Graphical Abstract, Highlights • Acute colitis triggers long-term events related to depression • Leukocytes infiltrate into brain vasculature • Luteolin abolishes leukocyte infiltration and visceral hypersensitivity • Luteolin abolishes depression-related behaviors, Pathophysiology; Behavioral Neuroscience; Cellular Neuroscience; Immunity

The gut microbiome consists of a multi-kingdom microbial community. Whilst the role of bacteria as causal contributors governing host physiological development is well established, the role of fungi remains to be determined. Here, we use germ-free mice colonized with defined species of bacteria, fungi, or both to differentiate the causal role of fungi on microbiome assembly, immune development, susceptibility to colitis, and airway inflammation. Fungal colonization promotes major shifts in bacterial microbiome ecology, and has an independent effect on innate and adaptive immune development in young mice. While exclusive fungal colonization is insufficient to elicit overt dextran sulfate sodium-induced colitis, bacterial and fungal co-colonization increase colonic inflammation. Ovalbumin-induced airway inflammation reveals that bacterial, but not fungal colonization is necessary to decrease airway inflammation, yet fungi selectively promotes macrophage infiltration in the airway. Together, our findings demonstrate a causal role for fungi in microbial ecology and host immune functionality, and therefore prompt the inclusion of fungi in therapeutic approaches aimed at modulating early life microbiomes., The immunomodulatory role of commensal gut fungi and interactions with bacteria remain unclear. Here, using germ-free mice colonized with defined species of bacteria and fungi, the authors find that fungal colonization induces changes in bacterial microbiome ecology while having an independent effect on innate and adaptive immunity in mice.

The mechanisms of epithelial wound healing are not completely understood, especially in the context of proteases and their receptors. It was recently shown that activation of protease-activated receptor-2 (PAR2) on intestinal epithelial cells induced the expression of cyclooxygenase-2 (COX-2), which has protective functions in the gastrointestinal tract. It was hypothesized that PAR2-induced COX-2 could enhance wound healing in intestinal epithelial cells. Caco2 cells were used to model epithelial wound healing of circular wounds. Cellular proliferation was studied with a 5-ethynyl-2'-deoxyuridine assay, and migration was studied during wound healing in the absence of proliferation. Immunofluorescence was used to visualize E-cadherin and F-actin, and the cellular transcription profile during wound healing and PAR2 activation was explored with RNA sequencing. PAR2 activation inhibited Caco2 wound healing by reducing cell migration, independently of COX-2 activity. Interestingly, even though migration was reduced, proliferation was increased. When the actin dynamics and cell-cell junctions were investigated, PAR2 activation was found to induce actin cabling and prevent the internalization of E-cadherin. To further investigate the effect of PAR2 on transcriptionally dependent wound healing, RNA sequencing was performed. This analysis revealed that PAR2 activation, in the absence of wounding, induced a similar transcriptional profile compared with wounding alone. These findings represent a novel effect of PAR2 activation on the mechanisms of epithelial cell wound healing that could influence the resolution of intestinal inflammation.

Significance: Shortly after the discovery of the role of hydrogen sulfide (H2S) in many physiological and pathological processes, attempts were made to develop novel pharmaceuticals that may be of benefit for treatment or prevention of a wide range of disorders. The promise of H2S-based therapeutics is now being demonstrated in clinical trials. Recent Advances: H2S-releasing drugs, such as SG1002 for cardiovascular disorders, and ATB-346 for arthritis, have progressed into clinical trials and have shown considerable promise. Some older drugs, such as zofenopril, have now been recognized to produce at least some of the beneficial effects through release of H2S. Critical Issues: There remains a need to better understand the underlying mechanisms for some of the observed effects of H2S-releasing drugs in a clinical setting, such as the marked increase in analgesic potency that has been observed with ATB-346. Future Directions: The proof-of-concept clinical studies reviewed herein pave the way for ex...

Cancer cell lines have been the mainstay of intestinal epithelial experimentation for decades, due primarily to their immortality and ease of culture. However, because of the inherent biological abnormalities of cancer cell lines, many cellular biologists are currently transitioning away from these models and toward more representative primary cells. This has been particularly challenging, but recent advances in the generation of intestinal organoids have brought the routine use of primary cells within reach of most epithelial biologists. Nevertheless, even with the proliferation of publications that use primary intestinal epithelial cells, there is still a considerable amount of trial and error required for laboratories to establish a consistent and reliable method to culture three-dimensional (3D) intestinal organoids and primary epithelial monolayers. We aim to minimize the time other laboratories spend troubleshooting the technique and present a standard method for culturing primary epithelial cells. Therefore, we have described our optimized, high-yield, cost-effective protocol to grow 3D murine colonoids for more than 20 passages and our detailed methods to culture these cells as confluent monolayers for at least 14 days, enabling a wide variety of potential future experiments. By supporting and expanding on the current literature of primary epithelial culture optimization and detailed use in experiments, we hope to help enable the widespread adoption of these innovative methods and allow consistency of results obtained across laboratories and institutions. NEW & NOTEWORTHY Primary intestinal epithelial monolayers are notoriously difficult to maintain culture, even with the recent advances in the field. We describe, in detail, the protocols required to maintain three-dimensional cultures of murine colonoids and passage these primary epithelial cells to confluent monolayers in a standardized, high-yield and cost-effective manner.

Objectives The objective of this study was to determine whether constipation-predominant irritable bowel syndrome (IBS-C) is associated with changes in intestinal barrier and secretory function. Methods A total of 19 IBS-C patients and 18 healthy volunteers (all females) underwent saccharide excretion assay (0.1 g 13C mannitol and 1 g lactulose), measurements of duodenal and colonic mucosal barrier (transmucosal resistance (TMR), macromolecular and Escherichia coli Bio-Particle translocation), mucosal secretion (basal and acetylcholine (Ach)-evoked short-circuit current (Isc)), in vivo duodenal mucosal impedance, circulating endotoxins, and colonic tight junction gene expression. Results There were no differences in the in vivo measurements of barrier function between IBS-C patients and healthy controls: cumulative excretion of 13C mannitol (0-2 h mean (s.e.m.); IBS-C: 12.1 (0.9) mg vs. healthy: 13.2 (0.8) mg) and lactulose (8-24 h; IBS-C: 0.9 (0.5) mg vs. healthy: 0.5 (0.2) mg); duodenal impedance IBS-C: 729 (65) Ω vs. healthy: 706 (43) Ω; plasma mean endotoxin activity level IBS-C: 0.36 (0.03) vs. healthy: 0.35 (0.02); and in colonic mRNA expression of occludin, zonula occludens (ZO) 1-3, and claudins 1-12 and 14-19. The ex vivo findings were consistent, with no group differences: duodenal TMR (IBS-C: 28.2 (1.9) Ω cm2 vs. healthy: 29.8 (1.9) Ω cm2) and colonic TMR (IBS-C: 19.1 (1.1) Ω cm2 vs. healthy: 17.6 (1.7) Ω cm2); fluorescein isothiocyanate (FITC)-dextran (4 kDa) and E. coli Bio-Particle flux. Colonic basal Isc was similar, but duodenal basal Isc was lower in IBS-C (43.5 (4.5) μA cm-2) vs. healthy (56.9 (4.9) μA cm-2), P=0.05. Ach-evoked ΔIsc was similar. Conclusions Females with IBS-C have normal colonic barrier and secretory function. Basal duodenal secretion is decreased in IBS-C.

Gut microbiomes make major contributions to the physiological and immunological development of the host, but the relative importance of their bacterial and fungal components, and how they interact, remain largely unknown. We applied carefully controlled experiments in gnotobiotic mice colonized with defined communities of bacteria, fungi, or both to differentiate the direct role of fungi on microbiome assembly, host development, and susceptibility to colitis and airway inflammation. Our results revealed that fungal colonization alone was insufficient to promote the intestinal anatomic and physiological changes seen in mice colonized by bacteria, and had limited impact on the fecal metabolome. However, fungal colonization promoted major shifts in bacterial microbiome ecology, and had an independent effect on the innate and adaptive immune development in young mice. Fungi further exacerbated some aspects of the inflammatory effects of the bacterial community during OVA-induced airway inflammation by promoting macrophage infiltration in the airway. Our results demonstrate a dominant ecological and physiological role of bacteria in gut microbiomes, but highlight fungi as an ecological factor shaping the assembly of the bacterial community and a direct capacity to impact immune system and modulate disease susceptibility. These findings demonstrate that studies focused on bacteria alone provide an incomplete portrayal on microbiome ecology and functionality, and prompt for the inclusion of fungi in human microbiome studies.

BACKGROUND: Impaired mucosal healing in the intestinal epithelium has been linked to inflammatory bowel disease (IBD). While the resolution of inflammation was historically perceived to be a passive process of mucosal healing, we have begun to appreciate that cells and mediators that have traditionally been considered pro-inflammatory, are also crucial in the resolution of inflammation. Specifically, recent evidence suggests that neutrophils, while important contributors to acute inflammation, are also key elements in the pro-resolution microenvironment that promotes mucosal healing in the inflamed gut. Our previous data have shown that administration of the dietary fibre, rhamnogalacturonan (RGal), reduces disease severity in a murine model of DSS colitis. Additionally, apical treatment of the Caco-2 human intestinal epithelial cell line with RGal induces an increase in transepithelial electrical resistance (TER) and accelerates wound-healing in vitro. AIMS: We hypothesized that RGal promotes a healing response in epithelial cells via the production of mediators that contribute to the establishment of a pro-resolution microenvironment. The aims of this project are to (1) Characterize the receptor(s) and signalling pathways activated by RGal in intestinal epithelial cells and (2) determine the ability of RGal to create a pro-resolution inflammatory milieu and mediate neutrophil-epithelial interactions. METHODS: In order to determine the transcriptionally dependent effects of RGal on epithelial function, Caco-2 monolayers were treated apically for 6, 12 and 24h with RGal, and RNA collected for transcriptome sequencing. Genes with changes in expression more than 3-fold were entered into Enrichr for pathway analysis. In order to confirm changes in protein expression from transcriptome sequencing data, Meso Scale Discovery (MSD) multi-array immunoassay was performed. RESULTS: RGal differentially induced changes in gene expression 6, 12 and 24h post-treatment. While RGal had no significant effect on tight junction gene expression 6h post-treatment, RGal upregulated the expression of inflammatory response genes including neutrophil regulatory genes (CXCL1, 243.9-fold; CXCL2, 15.2-fold; CXCL3, 58.8-fold; CXCL5, 57-fold; CXCL8, 515.6-fold; G-CSF, 18-fold; n=3; p

Barrier dysfunction is a characteristic of the inflammatory bowel diseases (IBD), Crohn's disease and ulcerative colitis. Understanding how the tight junction is modified to maintain barrier function may provide avenues for treatment of IBD. We have previously shown that the apical addition of serine proteases to intestinal epithelial cell lines causes a rapid and sustained increase in transepithelial electrical resistance (TER), but the mechanisms are unknown. We hypothesized that serine proteases increase barrier function through trafficking and insertion of tight junction proteins into the membrane, and this could enhance recovery of a disrupted monolayer after calcium switch or cytokine treatment. In the canine epithelial cell line, SCBN, we showed that matriptase, an endogenous serine protease, could potently increase TER. Using detergent solubility-based cell fractionation, we found that neither trypsin nor matriptase treatment changed levels of tight junction proteins at the membrane. In a fast calcium switch assay, serine proteases did not enhance the rate of recovery of the junction. In addition, serine proteases could not reverse barrier disruption induced by IFNγ and TNFα. We knocked down occludin in our cells using siRNA and found this prevented the serine protease-induced increase in TER. Using fluorescence recovery after photobleaching (FRAP), we found serine proteases induce a greater mobile fraction of occludin in the membrane. These data suggest that a functional tight junction is needed for serine proteases to have an effect on TER, and that occludin is a crucial tight junction protein in this mechanism.

Opioids remain the gold standard for the treatment of moderate to severe pain. However, their analgesic properties come with important side effects, including pruritus, which occurs frequently after systemic or neuraxial administration. Although part of the opioid-induced itch is mediated centrally, recent evidence shows that the opioid receptor system in the skin also modulates itch. The goal of our study was to identify the peripherally located transducer mechanisms involved in opioid-induced pruritus. Scratching behaviors in response to an intradermal injection of the mu-opioid receptor (MOR) agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) was quantified in mast cell-, PAR2- and TRPV1-deficient mice or following ablation of TRPV1+ sensory neurons. We found that mast cells−/−, PAR-2−/−, or TRPV1−/− mice still exhibit DAMGO-induced itch responses. However, we show that ablation of TRPV1+ neurons or acute TRPV1 activation by capsaicin abolishes DAMGO-induced itch. Overall, our work shows that peripheral DAMGO-induced itch is dependent on the presence of TRPV1-expressing pruriceptors, but not the TRPV1 channel itself. Activation of these fibers by capsaicin prevents the opioid-induced itch.

BACKGROUND: The inflammatory microenvironment in the gut contains a variety of proteases from numerous sources including inflammatory cells. We have been studying the ability of proteases to induce a switch in the colonic epithelium from a barrier to a repair phenotype (epithelial to mesenchymal transition [EMT]) characterized by increased migration and disrupted homeostasis. EMT involves the degradation of junctional proteins such as E-cadherin [Ecad], but the mechanisms by which Ecad is lost and the functional consequences of Ecad degradation remain incompletely understood. AIMS: To test the hypothesis that inflammatory proteases cleave Ecad to produce peptides that alter epithelial homeostasis by altering cell migration, proliferation, or cell death. METHODS: Ecad cleavage in vitro was determined using Western blot. Recombinant Ecad was incubated with neutrophil elastase [NE] in a cell-free system and 24 peptides identified by mass spectrometry were chosen for high-throughput screening based on frequency of occurrence, p-value scoring, and accessibility of cleavage sites. Peptides were synthesized and tested for biological activity including proliferation, cell death, and cell migration. Murine CMT-93 intestinal epithelial cells were cultured in 96 well plates and wounded 5 days post-confluency using the EssenBio WoundMaker™ tool. Wells were imaged simultaneously with the IncuCyte™ live-cell imaging system for 24–48 hours following exposure to 1, 10, or 100 µg/mL concentrations of peptides. Cells were transfected with a GFP marker to allow automated cell number tracking to measure proliferation. Cytotoxicity was determined using Cytotox dye which binds cells undergoing membrane degradation. All analysis was done using the IncuCyte™ ZOOM platform in conjunction with ImageJ software. RESULTS: Basolateral stimulation of human Caco2 and murine CMT93 cells with NE confirmed the ability of NE to produce C- and N-terminal Ecad fragments in vitro. Of the 24 synthesized Ecad peptides, we identified 10 that significantly influenced wound closure rates both positively and negatively. Two peptides significantly inhibited wound healing rate by 13–26% compared to vehicle controls at a concentration of 100 µg/mL. Six peptides (100 µg/mL) significantly increased wound healing rates by 7–11% and three peptides (10 µg/mL) significantly increased wound healing rates by 6–13% compared to vehicle controls. Preliminary results suggest several of these peptides may also have cytostatic or pro-proliferative activity. CONCLUSIONS: Our results suggest that degradation of cell junction proteins by inflammatory proteases can create bioactive peptides that alter epithelial homeostasis and alter cell migration. Our data reveal a novel pathway whereby epithelia respond to inflammatory tissue damage at the cellular level to alter a barrier phenotype to a more dynamic epithelium. FUNDING AGENCIES: CIHR

BACKGROUND: The beneficial effects of dietary fibre have been recognized for many years. These complex polysaccharides are indigestible and fermented by gut microbiota, promoting advantageous effects to intestinal mucosa indirectly. Polysaccharides also have direct effects on intestinal epithelial barrier function and we have previous shown that rhamnogalacturonan (RGal), a polysaccharide isolated from the plant Acmella oleracea, promotes barrier function in human colonic epithelial Caco-2 cells. However, the underlying mechanism of action of RGal remains unclear. AIMS: We aimed to investigate if RGal directly enhances intestinal epithelial barrier function through TLR4 activation. METHODS: Human TLR4/CD14/MD2 transfected HEK 293 reporter cells were incubated with RGal (1000 μg/ml) with/without C34 (TLR4 inhibitor, 10 ng/ml) for 24 hrs. Supernatants were collected and activation of TLR4 was detected by using the secreted alkaline phosphatase assay (Invivogen). LPS (10 ng/ml) was used as positive control. Caco-2 cells were seeded on Millicell supports for 6 days and treated apically with vehicle (0.01% DMSO in PBS) and C34 (100 ng/ml). After 1 hr, cells were mounted in Ussing chambers and treated apically with RGal (1000 μg/ml). Transepithelial electrical resistance (TER) and FITC-dextran flux were measured. In another set of experiments, the monolayers were treated apically with GF109203X (pan-PKC inhibitor, 500 nM), myristoylated PKCζ pseudosubstrate inhibitor (10 μM) and Go6976 (PKCα/β inhibitor, 10 nM) for 10 minutes before apical addition of RGal (1000 μg/ml). RESULTS: Incubation of TLR4-expressing HEK cells with RGal (1000 μg/ml) activated TLR4 at similar levels compared with LPS (10 ng/ml). In addition, C34 (10 ng/ml) significantly inhibited both RGal and LPS activation without altering cell viability (assessed via MTT assay). Apical treatment of cells with RGal increased TER and reduced FITC-dextran flux compared to control. C34 reversed the RGal effects in TER. The RGal-mediated decrease in macromolecular permeability was dependent on PKC but not on PKCζ or PKCα/β. CONCLUSIONS: These data suggest that RGal enhances intestinal epithelial barrier function through activation of TLR4 and the PKC signaling pathway. Elucidation of RGal mechanisms of action could lead to new approaches to the treatment of inflammatory bowel diseases. FUNDING AGENCIES: NSERC

Patients with systemic inflammatory diseases (e.g., rheumatoid arthritis, inflammatory bowel disease, chronic liver disease) commonly develop debilitating symptoms (i.e., sickness behaviors) that arise from changes in brain function. The microbiota-gut-brain axis alters brain function and probiotic ingestion can influence behavior. However, how probiotics do this remains unclear. We have previously described a novel periphery-to-brain communication pathway in the setting of peripheral organ inflammation whereby monocytes are recruited to the brain in response to systemic TNF-α signaling, leading to microglial activation and subsequently driving sickness behavior development. Therefore, we investigated whether probiotic ingestion (i.e., probiotic mixture VSL#3) alters this periphery-to-brain communication pathway, thereby reducing subsequent sickness behavior development. Using a well characterized mouse model of liver inflammation, we now show that probiotic (VSL#3) treatment attenuates sickness behavior development in mice with liver inflammation without affecting disease severity, gut microbiota composition, or gut permeability. Attenuation of sickness behavior development was associated with reductions in microglial activation and cerebral monocyte infiltration. These events were paralleled by changes in markers of systemic immune activation, including decreased circulating TNF-α levels. Our observations highlight a novel pathway through which probiotics mediate cerebral changes and alter behavior. These findings allow for the potential development of novel therapeutic interventions targeted at the gut microbiome to treat inflammation-associated sickness behaviors in patients with systemic inflammatory diseases. SIGNIFICANCE STATEMENT This research shows that probiotics, when eaten, can improve the abnormal behaviors (including social withdrawal and immobility) that are commonly associated with inflammation. Probiotics are able to cause this effect within the body by changing how the immune system signals the brain to alter brain function. These findings broaden our understanding of how probiotics may beneficially affect brain function in the context of inflammation occurring within the body and may open potential new therapeutic alternatives for the treatment of these alterations in behavior that can greatly affect patient quality of life.

© 2014 by The American Society for Biochemistry and Molecular Biology, Inc. Mucosal biopsies from inflamed colon of inflammatory bowel disease patients exhibit elevated epithelial apoptosis compared with those from healthy individuals, disrupting mucosal homeostasis and perpetuating disease. Therapies that decrease intestinal epithelial apoptosis may, therefore, ameliorate inflammatory bowel disease, but treatments that specifically target apoptotic pathways are lacking. Proteinase-activated receptor-2 (PAR2), a G protein-coupled receptor activated by trypsin-like serine proteinases, is expressed on intestinal epithelial cells and stimulates mitogenic pathways upon activation. We sought to determine whether PAR2 activation and signaling could rescue colonic epithelial (HT-29) cells from apoptosis induced by proapoptotic cytokines that are increased during inflammatory bowel disease. The PAR2 agonists 2-furoyl-LIGRLO (2f-LI), SLIGKV and trypsin all significantly reduced cleavage of caspase-3, -8, and -9, poly(ADP-ribose) polymerase, and the externalization of phosphatidylserine after treatment of cells with IFN-γ and TNF-α. Knockdown of PAR2 with siRNA eliminated the anti-apoptotic effect of 2f-LI and increased the sensitivity of HT-29 cells to cytokine-induced apoptosis. Concurrent inhibition of both MEK1/2 and PI3K was necessary to inhibit PAR2-induced survival. 2f-LI was found to increase phosphorylation and inactivation of pro-apoptotic BAD at Ser112 and Ser136 by MEK1/2 and PI3K-dependent signaling, respectively. PAR2 activation also increased the expression of anti-apoptotic MCL-1. Simultaneous knockdown of both BAD and MCL-1 had minimal effects on PAR2-induced survival, whereas single knockdown had no effect. We conclude that PAR2 activation reduces cytokine-induced epithelial apoptosis via concurrent stimulation of MEK1/2 and PI3K but little involvement of MCL-1 and BAD. Our findings represent a novel mechanism whereby serine proteinases facilitate epithelial cell survival and may be important in the context of colonic healing.

The CAG is a professional organization that seeks to promote the discipline of gastroenterology in Canada and internationally through a series of activities aligned with a Strategic Plan (renewed and updated every five years) in order to advance our mandate of (i) supporting and engaging in the study of the organs of the digestive tract in health and disease, (ii) promoting the advancement of the science and art of gastroenterology by providing leadership in patient care, research, education, and continuing professional development (CPD), and (iii) promoting and maintaining the highest ethical standards (https://www.cag-acg.org/about/what-is-the-cag/).

Aquaporin (AQP) 3 expression is altered in inflammatory bowel diseases, although the exact mechanisms regulating AQP abundance are unclear. Although interferon gamma (IFNγ) is centrally involved in intestinal inflammation, the effect of this cytokine on AQP3 expression remains unknown. HT-29 human colonic epithelial cells were treated with IFNγ to assess AQP3 mRNA expression by real-time RT-PCR and functional protein expression through the uptake of radiolabelled glycerol. Transient knockdown of signal transducer and activator of transcription 1 (STAT1), STAT3, Sp1, and Sp3 were performed to determine the involvement of these transcription factors in the IFNγ-induced signalling cascade. AQP3 promoter regions involved in the response to IFNγ were assessed using a luciferase reporter system. Likewise, enteroids derived from human colonic biopsies were also treated with IFNγ to assess for changes in AQP3 mRNA expression. IFNγ decreased AQP3 mRNA expression in HT-29 cells in a time- and concentration-dependent manner and reduced functional AQP3 protein expression (decreased 3H-labelled glycerol uptake). IFNγ also reduced AQP3 expression in enteroids derived from human colonic biopsies. Knockdown of STAT1 partially prevented the IFNγ-induced downregulation of AQP3 expression, whereas STAT3 and Sp3 knockdowns resulted in increased baseline expression of AQP3 but did not alter IFNγ-induced downregulation. Constitutive transcription of AQP3 is downregulated by IFNγ as demonstrated using the luciferase reporter system, with Sp3 bound to the AQP3 promoter as shown by chromatin immunoprecipitation. AQP3 constitutive transcription in intestinal epithelial cells is downregulated by IFNγ. This response requires STAT1 that is postulated to drive the downregulation of AQP3 expression through increased acetylation or decreased deacetylation the AQP3 promoter, ultimately resulting in decreased constitutive transcription of AQP3. • IFNγ suppresses the expression of AQP3 in intestinal epithelial cells. • Proximal AQP3 promoter elements are sufficient to drive constitutive expression and mediate the IFNγ-induced downregulation of AQP3 mRNA expression. • IFNγ-induced suppression of AQP3 is dependent upon STAT1 expression, but not STAT3, Sp1, or Sp3.

Changes in barrier function of the gastrointestinal tract are thought to contribute to the inflammatory bowel diseases Crohn's disease and ulcerative colitis. Previous work in our lab demonstrated that apical exposure of intestinal epithelial cell lines to serine proteases results in an increase in transepithelial electrical resistance (TER). However, the underlying mechanisms governing this response are unclear. We aimed to determine the requirement for proteolytic activity, epidermal growth factor receptor (EGFR) activation, and downstream intracellular signaling in initiating and maintaining enhanced barrier function following protease treatment using a canine intestinal epithelial cell line (SCBN). We also examined the role of phosphorylation of myosin regulatory light chain on the serine protease-induced increase in TER through. It was found that proteolytic activity of the serine proteases trypsin and matriptase is required to initiate and maintain the protease-mediated increase in TER. We also show that MMP-independent EGFR activation is essential to the sustained phase of the protease response, and that Src kinases may mediate EGFR transactivation. PI3-K and ERK1/2 signaling were important in reaching a maximal increase in TER following protease stimulation; however, their upstream activators are yet to be determined. CK2 inhibition prevented the increase in TER induced by serine proteases. The bradykinin B(2) receptor was not involved in the change in TER in response to serine proteases, and no change in phosphorylation of MLC was observed after trypsin or matriptase treatment. Taken together, our data show a requirement for ongoing proteolytic activity, EGFR transactivation, as well as downstream PI3-K, ERK1/2, and CK2 signaling in protease-mediated barrier enhancement of intestinal epithelial cells. The pathways mediating enhanced barrier function by proteases may be novel therapeutic targets for intestinal disorders characterized by disrupted epithelial barrier function.

Inflammatory diseases of the gut are associated with altered electrolyte and water transport, leading to the development of diarrhea. Epithelially expressed aquaporins (AQPs) are downregulated in inflammation, although the mechanisms involved are not known. We hypothesized that AQP3 expression in intestinal epithelial cells is altered in intestinal inflammation and that these changes are driven by tumor necrosis factor (TNF) α. Human colonic adenocarcinoma (HT‐29) cells were treated with TNF α to investigate signaling mechanisms in vitro. AQP3 expression was assessed by real‐time PCR and radiolabeled glycerol uptake, with select inhibitors and a luciferase reporter construct used to further elucidate intracellular signaling. AQP3 expression was downregulated in HT‐29 cells treated with TNF α. Luciferase reporter construct experiments revealed that TNF α downregulated constitutive transcriptional activity of the AQP3 promoter, and inhibition of MEK/ERK and nuclear factor κB (NF‐κB) signaling prevented the decrease in AQP3 mRNA expression. Constitutive AQP3 expression was suppressed by specificity protein (Sp) 3, and knockdown of this transcription factor bound to the AQP3 promoter was able to partially prevent the TNF α‐induced downregulation of AQP3. TNF α signals through MEK/ERK and NF‐κB to enhance the negative transcriptional control of AQP3 expression exerted by Sp3. Similar mechanisms regulate numerous ion channels, suggesting a common mechanism by which both ion and water transport are altered in inflammation.

BACKGROUND: It is well known that diet profoundly affects intestinal physiology, with some diets contributing to a “leaky gut”, possibly promoting IBD and metabolic syndrome. Recently, several studies have suggested that the enteric nervous system, composed of neurons and glial cells, could be a potent regulator of intestinal permeability. We hypothesize that nutrients, sensed at the level of the epithelium, could trigger a neuroglial response to regulate intestinal permeability. AIMS: We investigated whether nutrients acutely modulate intestinal permeability at the level of the small intestine and if the enteric nervous system plays a role in this effect. METHODS: Intact jejunum and Ileum segments from CD1 mice were mounted in Ussing chambers. Transepithelial electrical resistance (TER) and short circuit current (Isc) were recorded for 50 min after stimulation with different nutrients. Two different size probes, 400 Da Fluorescein isothiocyanate (FITC) or 4000 Da FITC-Dextran (FD4), were used as markers of intestinal permeability. Apical glucose, fructose, glutamine (10 mM) or 5% Intralipid® were used as nutrient stimuli. Enteric neurons were either inhibited with tetrodotoxin (TTX, 0.5 µM) or activated with veratridine (10 µM). Enteric gliotransmission was inhibited with the connexin 43 blocker Gap26 (20 µM). RESULTS: The nutrients used in this study were “sensed” by the intestinal epithelium as illustrated by a rapid change in Isc following stimulation (+14, +7, -28 µA/cm(2) for glucose, glutamine and Intralipid, respectively, in the jejunum; +132, +42, -14, -56 µA/cm(2) for glucose, glutamine, fructose and Intralipid in the ileum). Addition of 5% Intralipid to the luminal side increased TER in both jejunum (+10 Ω/cm(2)) and Ileum (+10 Ω/cm(2)). Glutamine triggered a significant (p

BACKGROUND: The barrier function of the intestinal epithelium is a first-line of defense that is compromised in IBD. We have shown that epithelia treated with dinitrophenol (DNP: uncouples oxidative phosphorylation) have a dramatic impairment in their barrier function, and internalize non-invasive commensal E. coli. Mitochondria do not function in isolation; they are closely aligned with the endoplasmic reticulum (ER). AIMS: To investigate the interaction of mitochondrial dysfunction, ER stress and autophagic processes as a key determinant of epithelial-bacterial interaction, transcellular permeability and the fate of commensal bacteria that gain access to the intracellular compartment as a consequence of metabolic stress. METHODS: METHODS: Human colonic biopsies were mounted in Ussing chambers, murine epithelial colonic organoids were re-suspended and grown as a monolayer, and human colon-derived epithelial cell lines were cultured on transwell filters or on plastic. Bacteria were added to the luminal buffer and the tissue treated with DNP ± the ER stressor, tunicamycin (TM), and bacterial internalization and translocation assessed. Mechanistic studies involved measuring ATP production, immunoblotting, assessment of LC3 activation for autophagy and gene knock-down (KD) by siRNA and CRISPR/cas9. RESULTS: RESULTS: DNP promoted the translocation and internalization of E. coli and, remarkably, TM reduced this barrier defect. TM did not prevent the DNP-evoked drop in ATP or the rate of epithelial update of inert beads, but E. coli, DNP and TM-treated cells had increased autophagy. The effect of TM was lost in cells lacking the autophagy protein, ATG16L1, suggesting that the ER-stress promoted killing of the internalized bacteria. Of the 3 major arms of the ER stress response, only KD of ATF6 ablated the TM antagonism of the DNP-evoked barrier effect; the increase in autophagy evoked by TM was absent in ATF6 KD epithelia. Pharmacological studies indicate that the kinase, DAPK1 is required from the ER stress-ATF6 signal to drive autophagy to kill the internalized E. coli. CONCLUSIONS: Conclusion: The ATF6 arm of ER stress antagonizes metabolic stress-induced decreases in epithelial barrier function to commensal bacteria by promoting xenophagy via upregulation of DAPK1. FUNDING AGENCIES: CAG, CIHRAIHS, HPI-NSERC, CNPq

NOT PUBLISHED AT AUTHOR’S REQUEST Funding Agencies: CIHRAlberta Innovates, Human Frontier Science Program

Background & Aims The 5-hydroxytryptamine receptor 4 (5-HT 4 R or HTR 4 ) is expressed in the colonic epithelium but little is known about its functions there. We examined whether activation of colonic epithelial 5-HT 4 R protects colons of mice from inflammation. Methods The 5-HT 4 R agonist tegaserod (1 mg/kg), the 5-HT 4 R antagonist GR113808 (1 mg/kg), or vehicle (control) were delivered by enema to wild-type or 5-HT 4 R knockout mice at the onset of, or during, active colitis, induced by administration of dextran sodium sulfate or trinitrobenzene sulfonic acid. Inflammation was measured using the colitis disease activity index and by histologic analysis of intestinal tissues. Epithelial proliferation, wound healing, and resistance to oxidative stress-induced apoptosis were assessed, as was colonic motility. Results Rectal administration of tegaserod reduced the severity of colitis compared with mice given vehicle, and accelerated recovery from active colitis. Rectal tegaserod did not improve colitis in 5-HT 4 R knockout mice, and intraperitoneally administered tegaserod did not protect wild-type mice from colitis. Tegaserod increased proliferation of crypt epithelial cells. Stimulation of 5-HT 4 R increased Caco-2 cell migration and reduced oxidative stress-induced apoptosis; these actions were blocked by co-administration of the 5-HT 4 R antagonist GR113808. In noninflamed colons of wild-type mice not receiving tegaserod, inhibition of 5-HT 4 Rs resulted in signs of colitis within 3 days. In these mice, epithelial proliferation decreased and bacterial translocation to the liver and spleen was detected. Daily administration of tegaserod increased motility in inflamed colons of guinea pigs and mice, whereas administration of GR113808 disrupted motility in animals without colitis. Conclusions 5-HT 4 R activation maintains motility in healthy colons of mice and guinea pigs, and reduces inflammation in colons of mice with colitis. Agonists might be developed as treatments for patients with inflammatory bowel diseases.

Proteinase-activated receptor (PAR)2, a G protein-coupled receptor activated by serine proteinases, has been implicated in both intestinal inflammation and epithelial proliferation. Cyclooxygenase (COX)-2 is overexpressed in the gut during inflammation as well as in colon cancer. We hypothesized that PAR2 drives COX-2 expression in intestinal epithelial cells. Treatment of Caco-2 colon cancer cells with the PAR2-activating peptide 2-furoyl-LIGRLO-NH2 (2fLI), but not by its reverse-sequence PAR2-inactive peptide, for 3 h led to an increase in intracellular COX-2 protein expression accompanied by a COX-2-dependent increase in prostaglandin E2 production. 2fLI treatment for 30 min significantly increased metalloproteinase activity in the culture supernatant. Increased epidermal growth factor receptor (EGFR) phosphorylation was observed in cell lysates following 40 min of treatment with 2fLI. The broad-spectrum metalloproteinase inhibitor marimastat inhibited both COX-2 expression and EGFR phosphorylation. The EGFR tyrosine kinase inhibitor PD153035 also abolished 2fLI-induced COX-2 expression. Although PAR2 activation increased ERK MAPK phosphorylation, neither ERK pathway inhibitors nor a p38 MAPK inhibitor affected 2fLI-induced COX-2 expression. However, inhibition of either Src tyrosine kinase signaling by PP2, Rho kinase signaling by Y27632, or phosphatidylinositol 3 (PI3) kinase signaling by LY294002 prevented 2fLI-induced COX-2 expression. Trypsin increased COX-2 expression through PAR2 in Caco-2 cells and in an EGFR-dependent manner in the noncancerous intestinal epithelial cell-6 cell line. In conclusion, PAR2 activation drives COX-2 expression in Caco-2 cells via metalloproteinase-dependent EGFR transactivation and activation of Src, Rho, and PI3 kinase signaling. Our findings provide a mechanism whereby PAR2 can participate in the progression from chronic inflammation to cancer in the intestine.

Both pathogenic and commensal strains of Escherichia coli colonize the human intestinal tract. Pathogenic strains differ only in the expression of virulence factors, many of which comprise a type III secretion system (TTSS). Little is known regarding the effect of E. coli on the intestinal epithelial response to the secretagogues that drive ion secretion, despite its importance in causing clinically significant diarrhoea. Using Ussing chambers to measure electrogenic ion transport of T84 intestinal epithelial cell monolayers, we found that all strains of E. coli tested (pathogenic, commensal, probiotic and lab strain) significantly reduced cAMP-dependent ion secretion after 4-8 h exposure. Enteropathogenic E. coli mutants lacking a functional TTSS caused similar hyposecretion while not causing significant apoptosis (as shown by caspase-3 cleavage) or necrosis (lactate dehydrogenase release), as did the commensal strain F18, indicating that epithelial cell death was not the cause of hyposecretion. Enteropathogenic E. coli and the TTSS mutant significantly reduced cell surface expression of the apical anion channel, cystic fibrosis transmembrane conductance regulator, which is likely the mechanism behind the pathogen-induced hyposecretion. However, F18 did not cause cystic fibrosis transmembrane conductance regulator mislocalization and the commensal-induced mechanism remains unclear.

BACKGROUND: The inflammatory microenvironment in the gut contains a variety of proteases which are known to be increased in patient samples in both IBD and CRC. How these proteases and their proteolytic peptide products contribute to wound resolution has been poorly elucidated. A cellular switch from a “barrier” to a “migration/repair” phenotype is required for healing in IBD, but is also a hallmark of tumorigenesis. Proteolytic degradation of epithelial E-cadherin (Ecad) is necessary for this process, we have been studying the biological activity small peptide fragments of Ecad generated by neutrophil elastase, an inflammatory protease elevated in IBD. We have been studying the ability of proteases to induce a switch in the colonic epithelium from a barrier to a repair phenotype (epithelial to mesenchymal transition [EMT]) characterized by increased migration and disrupted homeostasis. AIMS: To test the hypothesis that inflammatory proteases process Ecad into small bioactive peptides that contribute to wound resolution. METHODS: Recombinant Ecad was incubated with neutrophil elastase (NE) in vitro to produce NE-dependent Ecad peptides. Six of these peptides shared partial homology with Ecad peptides identified by mass spectrometry in IBD patient samples, and were chosen for further characterization. Peptides were synthesized and assayed for their ability to alter wound healing capacity, proliferation, cell spreading, and cytotoxicity in Caco-2 cells using the IncuCyte™ live-cell imaging system for 48 hours following exposure to 1, 10, and 100 mg/mL concentrations of peptides. All analysis was done using the IncuCyte™ ZOOM platform in conjunction with ImageJ software. RESULTS: We have identified 6 Ecad peptides produced by neutrophil elastase activity that appear to be increased in IBD patient tissue. We have characterized these peptides to have novel biological roles in altering wound resolution and proliferation rates, with 3 peptides showing significantly increased wound healing capacity at at least one concentration. These 3 peptides (KAADTDPTAPPYD, NRNTGVISVV, and LPPEDDTRDNV) showed improved wound closures of approximately 7–10% under serum free conditions and 5–10% under full serum conditions compared to controls. Preliminary data also suggests that these peptides appear to have a positive effect on proliferation rates, and appear to alter cellular morphology of cells to that of a more flattened cell type, typical of repair programming of cells to cover a denuded area. CONCLUSIONS: Our data reveal a novel role for proteolytic processing of Ecad under inflammatory conditions, producing bioactive peptides that drive a wound-healing phenotype in epithelial cells in response to damage. FUNDING AGENCIES: CIHRUniversity of Calgary Faculty Seed Grants

Serine proteases play important physiological roles through their activity at G protein-coupled protease-activated receptors (PARs). We examined the roles that specific phospholipase (PL) C and protein kinase (PK) C (PKC) isoforms play in the regulation of PAR2-stimulated chloride secretion in intestinal epithelial cells. Confluent SCBN epithelial monolayers were grown on Snapwell supports and mounted in modified Ussing chambers. Short-circuit current ( Isc) responses to basolateral application of the selective PAR2 activating peptide, SLIGRL-NH2, were monitored as a measure of net electrogenic ion transport caused by PAR2 activation. SLIGRL-NH2 induced a transient Isc response that was significantly reduced by inhibitors of PLC (U73122), phosphoinositol-PLC (ET-18), phosphatidylcholine-PLC (D609), and phosphatidylinositol 3-kinase (PI3K; LY294002). Immunoblot analysis revealed the phosphorylation of both PLCβ and PLCγ following PAR2 activation. Pretreatment of the cells with inhibitors of PKC (GF 109203X), PKCα/βI (Gö6976), and PKCδ (rottlerin), but not PKCζ (selective pseudosubstrate inhibitor), also attenuated this response. Cellular fractionation and immunoblot analysis, as well as confocal immunocytochemistry, revealed increases of PKCβI, PKCδ, and PKCε, but not PKCα or PKCζ, in membrane fractions following PAR2 activation. Pretreatment of the cells with U73122, ET-18, or D609 inhibited PKC activation. Inhibition of PI3K activity only prevented PKCδ translocation. Immunoblots revealed that PAR2 activation induced phosphorylation of both cRaf and ERK1/2 via PKCδ. Inhibition of PKCβI and PI3K had only a partial effect on this response. We conclude that basolateral PAR2-induced chloride secretion involves activation of PKCβI and PKCδ via a PLC-dependent mechanism resulting in the stimulation of cRaf and ERK1/2 signaling.

We examined the stimulus-secretion pathways whereby proteinase-activated receptor 2 (PAR-2) stimulates Cl− secretion in intestinal epithelial cells. SCBN and T84 epithelial monolayers grown on Snapwell supports and mounted in modified Ussing chambers were activated by the PAR-2-activating peptides SLIGRL-NH2 and 2-furoyl-LIGRLO-NH2. Short-circuit current ( Isc) was used as a measure of net electrogenic ion transport. Basolateral, but not apical, application of SLIGRL-NH2 or 2-furoyl-LIGRLO-NH2 caused a concentration-dependent change in Isc that was significantly reduced in Cl−-free buffer and by the intracellular Ca2+ blockers thapsigargin and BAPTA-AM, but not by the Ca2+ channel blocker verapamil. Inhibitors of PKA (H-89) and CFTR (glibenclamide) also significantly reduced PAR-2-stimulated Cl− transport. PAR-2 activation was associated with increases in cAMP and intracellular Ca2+. Immunoblot analysis revealed increases in phosphorylation of epidermal growth factor (EGF) receptor (EGFR) tyrosine kinase, Src, Pyk2, cRaf, and ERK1/2 in response to PAR-2 activation. Pretreatment with inhibitors of cyclooxygenases (indomethacin), tyrosine kinases (genistein), EGFR (PD-153035), MEK (PD-98059 or U-0126), and Src (PP1) inhibited SLIGRL-NH2-induced increases in Isc. Inhibition of Src, but not matrix metalloproteinases, reduced EGFR phosphorylation. Reduced EGFR phosphorylation paralleled the reduction in PAR-2-stimulated Isc. We conclude that activation of basolateral, but not apical, PAR-2 induces epithelial Cl− secretion via cAMP- and Ca2+-dependent mechanisms. The secretory effect involves EGFR transactivation by Src, leading to subsequent ERK1/2 activation and increased cyclooxygenase activity.

Chronic inflammation of mucosae is associated with an increased cancer risk. Tumorigenesis in these tissues is associated with the activity of some proteinases, cyclooxygenase-2 (COX-2), and beta-catenin. Serine proteinases participate in both inflammation and tumorigenesis through the activation of proteinase-activated receptor-2 (PAR(2)), which up-regulates COX-2 by an unknown mechanism. We sought to determine whether beta-catenin participated in PAR(2)-induced COX-2 expression and through what cellular mechanism. In A549 epithelial cells, we showed that PAR(2) activation increased COX-2 expression through the beta-catenin/T cell factor transcription pathway. This effect was dependent upon ERK1/2 MAPK, which inhibited the beta-catenin-regulating protein, glycogen synthase kinase-3beta, and induced the activity of the cAMP-response element-binding protein (CREB). Knockdown of CREB by small interfering RNA revealed that PAR(2)-induced beta-catenin transcriptional activity and COX-2 expression were CREB-dependent. A co-immunoprecipitation assay revealed a physical interaction between CREB and beta-catenin. Thus, PAR(2) up-regulated COX-2 expression via an ERK1/2-mediated activation of the beta-catenin/Tcf-4 and CREB pathways. These findings reveal new cellular mechanisms by which serine proteinases may participate in tumor development and are particularly relevant to cancers associated with chronic mucosal inflammation, where serine proteinases are abundant and COX-2 overexpression is a common feature.

The life expectancy for cystic fibrosis (CF) patients has increased dramatically over the last 30 years. Although the overall cancer risk for CF patients does not appear to be increased there is a marked increased risk of gastrointestinal malignancies especially in the post lung transplant population. CF patients that do develop gastrointestinal malignancies do so at an earlier age and there is often a lag in the diagnosis and management of these individuals. We present a 39 year old male CF patient that underwent a colonoscopy for colon cancer screening and a large, near obstructing, villous adenoma of his ileum was found. The polyp was removed successfully via endoscopy without incident and there was no evidence of malignancy. An upper endoscopy revealed a long segment of Barrett's esophagus with no evidence of dysplasia. We present this case as well as a detailed review of the literature on cancer risk in CF and a discussion of the mechanisms that may be involved. We also present the risk of GI malignancies in non-CF patients as a guide on how to assess and manage the risk of GI malignancies in this ever-changing patient population.