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sTu1736

IL-33/ST2 Axis Modulates Epithelial Repair and Gut Mucosal Wound Healingin DSS-Colitic MiceLoris Riccardo Lopetuso, Carlo De Salvo, Henry N. Senkfor, Xiao-Ming Wang, DerekAbbott, Franco Scaldaferri, Antonio Gasbarrini, Theresa T. Pizarro

Background. Increasing evidence confirms that IL-33 and its receptor, ST2, are importantfactors in the pathogenesis of IBD. However, animal studies have yielded ambiguous results,reporting both pathogenic as well as protective functions. The aim of our study was tocharacterize and functionally evaluate the precise role of the IL-33/ST2 axis following acuteepithelial injury and mucosal repair in dextran sodium sulphate (DSS)-induced colitic mice.Methods. 3% DSS was administered for 5d to C57/BL6 wild-type (WT), IL-33 KO and ST2KO mice to induce colitis. DSS was then replaced with regular drinking water for 2 wks(recovery period). Another group of WT mice received DSS for 5d and IL-33 (33ug/kg, i.p.)or vehicle (VEH) every other day during the recovery period. Mice were sacrificed eitherafter DSS challenge or after 1 or 2 wks of recovery; control mice (CT) not exposed to DSSwere sacrificed at similar time points, at which time colons were harvested. Body weight,occult blood test, and stool consistency were measured daily to calculate Disease ActivityIndex (DAI), and endoscopic and histological evaluation of colons were performed usingestablished scoring systems. IHC, qPCR and Western blots were done on full-thicknesscolons for IL-33 and ST2 localization, mRNA expression, and evaluation of protein isoforms,respectively. Results. DSS administered to WT mice resulted in increased body weight lossand DAI. More severe colitis was observed following DSS+1wk recovery vs. after 5d ofDSS, which decreased after DSS+2wks recovery. IL-33 mRNA transcripts were dramaticallyelevated after DSS, and even more so following DSS+recovery vs. CT, but similar to CTafter DSS+2wks recovery. ST2 mRNA expression was also increased after DSS+recovery vs.CT, while no difference was found between 5d of DSS challenge and CT and after DSS+2wksrecovery. Full-length, bioactive IL33 (31 kDa), ST2L (76 kDa) and sST2 (52 kDa) wereexpressed in all experimental groups; the cleaved, less active form of IL33 (24 kDa) wasincreased in only DSS exposed mice vs. CT. IHC showed intense IL-33 and ST2 stainingwithin the inflamed and ulcerated mucosa of DSS-treated mice. ST2 staining was more evidentduring the recovery phase following DSS, notably localized to subepithelial myofibroblasts inclose proximity to areas of re-epithelialization. Remarkably, both IL-33 and ST2 KO miceshowed increased colonic inflammation after 2 wks recovery compared to after 5d DSS andvs also WT, suggesting the importance of IL-33/ST2 axis in mucosal healing. Likewise, IL-33 treatment of WT mice resulted in increased body weight, reduced DAI, and decreasedcolonic inflammation after 2 wks recovery vs. VEH. Conclusions. Our results suggest thatactivation of the IL-33/ST2 axis promotes epithelial repair and mucosal healing followingacute epithelial injury during DSS-induced colitis.

Tu1737

IL-1β Inhibits Contraction of Intestinal Lymphatic Smooth Muscle -Implications for Chronic Gut InflammationMahmoud Al-Kofahi, Judith L. Palmer Castor, Matthew Woolard, Ikuo Tsunoda, YupingWang, Moheb Boktor, Paul A. Jordan, Ankur Sheth, David C. Zawieja, MariappanMuthuchamy, Pierre-Yves von der Weid, Dmitry Ostanin, Kavya Pinto, Felix Becker

Introduction. IL-1β, IFN-γ and TNF-α have been implicated as mediators in chronic inflam-matory bowel diseases (IBD). The lymphatic system maintains tissue homeostasis by draininginterstitial fluid, inflammatory cells and cytokines using a system of lymphatic pumps,termed ‘lymphangions'. The failure of lymphatic pumps to clear inflammatory cytokinescreates a devastating positive-feedback loop which leads to inflammatory cytokine accumula-tion in tissues resulting in progression to chronic gut inflammation. However, the factorswhich cause lymphatic pump failure in IBD remain unknown. Methods. We studied theeffect of inflammatory cytokines (IL-1β, IFN-γ and TNF-α) and IBD conditioned mediumon intestinal lymphatic smooth muscle tonic contractility in vitro using a high through-putgel contraction assay. We examined mesenteric lymphatic smooth muscle contractility incollagen gels over 5 days in response to TNF−α (0-20 ng/ml), IFN−γ (0-1000 U/ml) and IL-1β (0-20 ng/ml) and IBD conditioned media. Results. We found that IL-1β dose-dependentlyimpaired gel contraction at 20 ng/ml, significantly reducing smooth muscle contraction,lower doses (5, 10 ng/ml) also reduced contraction (not sig.). By comparison, TNF−α andIFN−γ treated gels showed no differences in contraction at any concentration tested. OnlyIL-1β significantly increased COX-2 protein levels in lymphatic smooth muscle (vs. control).Conversely, COX-2 inhibition reversed the IL-1β relaxing effect, allowing smooth muscleto contract to the same levels as control. In contrast, COX-1 inhibition had no effect onlymphatic contractility. Only IL-1β (but not TNF-α or IFN−γ) significantly increased PGE2levels (vs. control). Therefore, IL-1β appears to mediate mesenteric lymphatic relaxation ina COX-2 dependent fashion via increased PGE2 levels. Conclusions. IL-1β appears to bean important regulatory modulator of lymphatic contraction which may contribute to thepathogenesis of IBD. These are the first data that show lymphatic smooth muscle contractilitycan be impaired by IL-1β and suggest that this type of high-throughput approach will helpidentify molecular mechanisms, which interfere with lymphatic smooth muscle function.This work supported by Department of Defense Grant ‘Lymphatic Vascular Based Therapyin IBD' (W81XWH-11-1-0577)

Tu1738

Effects of the Artificial Sweetener, Splenda®, in Experimental Crohn's DiseaseAndrew Harding, Alexander Rodriguez-Palacios, Lindsey Kaydo, Kourtney P. Nickerson,Wei Xin, Colleen M. Croniger, Christine McDonald, Fabio Cominelli

Background & Aims: The pathogenesis of Crohn's disease (CD) involves genetic and environ-mental factors, including alterations of the gut microbiota. Previous studies have suggestedthat Splenda®, a common artificial sweetener, alters the composition of the gut commensalflora. In addition, we have recently shown that maltodextrin, the bulking agent used inSplenda®, enhances biofilm formation and adherence of enteric flora to the intestinalepithelium in vitro. Sucralose, the non-nutritive sweetener in Splenda®, has also been shown

S-830AGA Abstracts

to alter glycemic responses in obese patients. The aim of this study was to investigate theeffects of Splenda® on intestinal inflammation, commensal flora, and glucose homeostasisin SAMP1/YitFc (SAMP) mice with experimental CD. Methods: SAMP and parental AKRcontrol mice were administered Splenda® in drinking water at 1.08 or 3.5 mg/ml (basedon the FDA acceptable daily intake of sucralose) or at 35 mg/ml, a dose exceeding the FDArange. Control SAMP and AKR mice received drinking water only. After 6 wks, ileum andcolon tissues were harvested and intestinal inflammation was assessed using stereomicros-copy, histology, and myeloperoxidase (MPO) activity (a biochemical marker of intestinalinflammation). Gut bacteria were analyzed by sub-culturing fecal bacteria onto selectivemedia, by qPCR of 16S rRNA, and by fluorescence in situ hybridization (FISH). Finally,systemic inflammation was evaluated by serum TNF-α levels and glycemic responses assessedby glucose tolerance tests. Results: Evaluation of ilea by stereomicroscopy and histologyshowed no significant differences in either percentages of abnormal mucosa or total inflamma-tory scores between all groups (n=18). However, ileal MPO activity was increased in SAMPtreated with 3.5 mg/mL Splenda® compared to water (219.1 vs. 81.8 U/g, p=0.022). FISHanalysis showed increased number of bacteria in the ileum of Splenda®-treated SAMPcompared to untreated control SAMP, with and increased Bacteroidetes:Firmicutes ratioassociated with increased Lactobacillus and decreased E. coli levels. In addition, differencesin fecal bacterial composition were detected in cultures of low abundant coliforms. Finally,serum TNF-alpha levels and glucose tolerance tests showed no differences between Splenda®-treated and control mice. Conclusions: Our study shows that all doses of Splenda® testeddid not significantly affect macroscopic or histologic severity of ileitis and glucose toleranceor serum TNF-α levels in SAMP mice with CD-like ileitis. However, our results suggest thatSplenda® may increase inflammatory activity at the biochemical level, together with changesin microbial-host interactions within the intestinal mucosa. Thus, daily use of artificialsweeteners, such as Splenda®, may play a role in exacerbation of disease activity in CD.

Tu1739

TGF-Beta Signaling in Dendritic Cells Mediates Crosstalk With Other InnateImmune Cells by Inducing the Production of Cytokines Important in MucosalProtectionRajalakshmy Ramalingam, Rita-Marie T. McFadden, Monica T. Midura-Kiela, Fayez K.Ghishan, Pawel R. Kiela

Background: We have previously shown that TRL4 stimulation leads to a refractory responseto TGFβ in dendritic cells (DCs) in vitro and that selective loss of TGFβ signaling in DCsin conditional TGFβ Type II receptor knockout mice (DC-Tgfbr2) leads to increased activationof T cells and autoimmunity. However, DCs interact with other innate immune cells toprovide the first line of defense against infection and to translocating commensal bacteriaduring mucosal injury. The mechanisms that mediate this crosstalk are not clearly understood.Aim & Methods: To study the effects of defective TGFβ signaling in DCs on the innateimmune response to epithelial barrier injury, we crossed DC-Tgfbr2 mice with into a Rag2-/-

background, thus generating Cre-DC-Tgfbr2/Rag2-/- (Cre- DKO) and Cre+Tgfbr2/Rag2-/- (Cre+

DKO) mice and treated them with water or 2% dextran sodium sulfate (DSS) for 5 days.Mice were monitored daily for body weight changes, stool consistency and rectal bleedingand were sacrificed either on day 5 or when they lost 15-20% of their original bodyweight. Colon weight/length ratio was calculated, and the degree of colitis was assessed byhistopathology, and cytokine expression in colonic mucosa and MLN by qPCR. Results:Compared to DSS-treated Cre- DKO, Cre+ DKO mice treated with 2% DSS exhibited signifi-cantly more severe phenotype with faster and greater body weight loss; about 50% of Cre+

DKO mice had to be sacrificed on day 4. All DSS-treated mice had rectal bleeding andincreased colon weight/length ratio as compared to untreated mice. Histological analysis ofthe colon revealed severe inflammation and infiltration of the distal colon, extensive mucosalerosions cells and complete loss of goblet cells. Both DSS-treated Cre- DKO and Cre+ DKOmice had similar neutrophilic infiltration based on the H&E analysis and MMP8 mRNAexpression. Although Cre- DKO showed significant increase in mucosal expression of IL-22 and IL-17a, cytokines derived from innate lymphoid cells and neutrophils, this increasewas not observed in DSS-treated Cre+ DKO mice. Conclusions: Loss of TGFβ signaling inDCs leads to increased susceptibility to mucosal injury likely due to deficient productionof IL-22 and IL-17a, cytokines produced by resident innate lymphoid cells and infiltratingneutrophils and implicated in mucosal protection during epithelial barrier breach. Althoughthe exact mechanism and the type of innate immune cells affected are still under investigation,loss of TGFβ signaling in DCs as an initial step in mucosal inflammation may lead toinsufficient initial protective innate immune responses and contribute to the establishmentof chronic disease.

Tu1740

NADPH Oxidase 1 (NOX1) Expressed in Colonic Macrophages Plays a CrucialRole in Trinitrobenzene Sulfonic Acid (TNBS)-Induced Colonic Inflammationin MiceHaruka Yokota, Daichi Utsumi, Hiroyo Nakajima, Riho Tanaka, Mari Yamada, YuyaTanaka, Kikuko Amagase, Shinichi Kato

Background & Aim: NADPH oxidase 1 (NOX1) was identified as non-phagocytic homologsof gp91Phox (NOX2), which originally found as a major source of reactive oxygen species(ROS) in phagocytes. Although NOX1 has been shown to be highly expressed in thegastrointestinal tract, especially the colon, the physiological and pathophysiological roles ofthis enzyme are not fully understood. In the present study, we investigated the role ofNOX1 in the pathogenesis of colonic inflammation using NOX1 knockout (NOX1KO) mice.Methods: Experimental colitis was induced in male NOX1KO and littermate wildtype (WT)mice by intrarectal injection of trinitrobenzene sulfonic acid (TNBS; 3 mg/mouse). Theseverity of colitis was evaluated macroscopically and histologically, and colonic myeloperoxi-dase (MPO) activity and reactive oxygen species (ROS) production were determined 4days after TNBS injection. The mRNA expression of various inflammatory mediators wasdetermined using real-time RT-PCR 4 days after TNBS injection. In vitro experiments werealso performed for isolated peritoneal and colonic lamina propria macrophages fromNOX1KO and WT mice. The cells were treated with lipopolysaccharide (LPS; 0.1 μmol/L),