Carolyn A. Sullivan

Role of STAT6 and Mast Cells in IL-4- and IL-13-Induced Alterations in Murine Intestinal Epithelial Cell Function

Gastrointestinal nematode infections generally invoke a type 2 cytokine response, characterized by the production of IL-4, IL-5, IL-9, and IL-13. Among these cytokines, IL-4 and IL-13 exhibit a functional overlap that can be explained by the sharing of a common receptor or receptor component (IL-4Rα). Binding of IL-4 by either the type 1 or 2 IL-4R, or of IL-13 by the type 2 IL-4R, initiates Jak-dependent tyrosine phosphorylation of the IL-4Rα-chain and the transcription factor, STAT6. In the present study, we investigated: 1) whether IL-13 has effects on intestinal epithelial cells similar to those observed with IL-4, and 2) whether the effects of IL-4 and IL-13 depend on STAT6 signaling and/or mast cells. BALB/c, STAT6−/−, and mast cell-deficient W/Wv mice or their +/+ littermates were treated with a long-lasting formulation of recombinant mouse IL-4 (IL-4C) or with IL-13 for seven days. Segments of jejunum were mounted in Ussing chambers to measure mucosal permeability; chloride secretion in response to PGE2, histamine, 5-hydroxytryptamine, or acetylcholine; and Na+-linked glucose absorption. IL-4C and IL-13 increased mucosal permeability, decreased glucose absorption, and decreased chloride secretion in response to 5-hydroxytryptamine. These effects were dependent on STAT6 signaling. Responses to PGE2 and histamine, which were dependent on mast cells and STAT6, were enhanced by IL-4C, but not by IL-13. The effects of IL-4 and IL-13 on intestinal epithelial cell function may play a critical role in host protection against gastrointestinal nematodes.

The Role of IL-4 in Heligmosomoides polygyrus-Induced Alterations in Murine Intestinal Epithelial Cell Function

IL-4 and IL-13 promote gastrointestinal worm expulsion, at least in part, through effects on nonlymphoid cells, such as intestinal epithelial cells. The role of IL-4/IL-13 in the regulation of intestinal epithelial function during Heligmosomoides polygyrus (Hp) infection was investigated in BALB/c mice infected with Hp or treated with a long-lasting formulation of recombinant mouse IL-4/αIL-4 complexes (IL-4C) for 7 days. Separate groups of BALB/c mice were drug-cured of initial infection and later reinfected and treated with anti-IL-4R mAb, an antagonist of IL-4 and IL-13 receptor binding, or with a control mAb. Segments of jejunum were mounted in Ussing chambers, and short circuit current responses to acetylcholine, histamine, serotonin, PGE2, and glucose were determined. Although only modest changes in epithelial cell function were observed during primary Hp infection, IL-4C or a secondary Hp infection each induced more dramatic changes, including increased mucosal permeability, reduced sodium-linked glucose absorption, and increased Cl− secretory response to PGE2. Some, but not all, effects of IL-4C and Hp infection were dependent on enteric nerves. Hp-induced changes in epithelial function were attenuated or prevented by anti-IL-4R mAb. Thus, IL-4/IL-13 mediate many of the effects of Hp infection on intestinal epithelial cell function and do so both through direct effects on epithelial cells and through indirect, enteric nerve-mediated prosecretory effects. These immune system-independent effector functions of IL-4/IL-13 may be important for host protection against gastrointestinal nematodes.

Anti-Inflammatory Mechanisms of Enteric Heligmosomoides polygyrus Infection against Trinitrobenzene Sulfonic Acid-Induced Colitis in a Murine Model

ABSTRACT Recent studies showed that enteric helminth infection improved symptoms in patients with inflammatory bowel disease as well as in experimental models of colitis. The aim of this study was to determine the mechanism of the protective effect of helminth infection on colitis-induced changes in immune and epithelial cell function. BALB/c mice received an oral infection of Heligmosomoides polygyrus third-stage larvae, were given intrarectal saline or trinitrobenzene sulfonic acid (TNBS) on day 10 postinfection, and were studied 4 days later. Separate groups of mice received intrarectal saline or TNBS on day 10 and were studied on day 14. Muscle-free colonic mucosae were mounted in Ussing chambers to measure mucosal permeability and secretion. Expression of cytokines was assessed by quantitative real-time PCR, and mast cells were visualized by immunohistochemistry. TNBS-induced colitis induced mucosal damage, upregulated Th1 cytokines, and depressed secretory responses. Heligmosomoides polygyrus elevated Th2 cytokine expression, increased mast cell infiltration and mucosal resistance, and also reduced some secretory responses. Prior H. polygyrus infection prevented TNBS-induced upregulation of Th1 cytokines and normalized secretory responses to specific agonists. TNBS-induced colitis did not alter H. polygyrus-induced mast cell infiltration or upregulation of Th2 cytokine expression. The results indicate that the protective mechanism of enteric nematode infection against TNBS-induced colitis involves prevention of Th1 cytokine expression and improved colonic function by a mechanism that may involve mast cell-mediated protection of neural control of secretory function. Similar response patterns could account for the clinical improvement seen in inflammatory bowel disease with helminthic therapy.

In situ expression of cagA and risk of gastroduodenal disease in Helicobacter pylori-infected children.

Background and Aim: Gastroduodenal disease is more common among adults and children with cagA+ Helicobacter pylori infection, but disease severity varies among those infected with cagA+ strains. We examined whether cagA in situ expression can predict disease manifestations among H pylori–infected children. Patients and Methods: Fifty-one children were selected from 805 patients with abdominal symptoms who underwent esophagogastroduodenoscopy with gastric biopsies. Endoscopic and histologic gastritis were scored and H pylori colonization was quantified by Genta stain and in situ hybridization expression of 16S rRNA and cagA. Results: Endoscopy was either normal (n = 14) or demonstrated nodularity (n = 18), gastric ulcer (n = 8) or duodenal ulcer (n = 11). H pylori was present in 7, 18, 6, and 10 children, respectively. Expression of 16S rRNA and cagA were significantly higher in children with ulcer compared with normal children. The fraction of H pylori bacteria expressing cagA in situ was higher in children with ulcer compared to those with endoscopic nodularity (P < 0.05). Conclusions: Thus, cagA in situ expression is increased in H pylori–infected children with peptic ulcers and may play a role in the pathogenesis of peptic ulcer disease during childhood. Determination of in situ expression of cagA complements traditional isolation and in vitro testing of single-colony isolates.

Munchausen Syndrome by Proxy: 1990: A Portent for Problems?

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. Munchausen syndrome by proxy is a form of child abuse in which parents fabricate or induce illness in their children. Health care providers, deceived by the parental history, contribute to the abuse by performing unnecessary

S1746 Rethinking the Role of IL-13 in Chronic 2,4,6-Trinitrobenzene Sulfonic Acid (TNBS) Colitis Induced Fibrosis

BACKGROUND: Mast cells play a key role in the pathophysiology of inflammatory bowel disease (IBD). Tranilast, N-(3,4-dimethoxycinnamoyl) anthranilic acid, a mast cell stabilizer, has been empirically used for IBD in Japan. The mechanism of tranilast in the improvement of IBD, however, has not yet been clearly delineated, and requires further investigation. Recently, heme oxygenase (HO)-1 has attracted attention in the pro-inflammationmechanism of tranilast. Aim: To investigate the role of tranilast for the treatment of IBD, and elucidated the mechanism and involvement of HO-1 in this effect, we administered tranilast intrarectally to dextran sulfate sodium (DSS)-induced colitis in mice. METHODS: Colitis was induced in C57BL/6(B6) mice by adding 3% DSS in drinking water ad libium for 5 days. Tranilast was administered by enema on day 0, day 2, and day 4 after induction of colitis. The disease activity index (DAI) and degree of colon injury were determined to know the clinical course of colitis. Toluidine blue staining was carried out to identify the mast cell. Staining for HO1 with immunofluorescence to evaluate the expression of HO-1 in the colon. Total RNA was extracted from colon specimens with quantitative reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Tranilast ameliorated DSS colitis clinically and pathologically with decreased number and degranulation of mast cells in the colon of DSS colitis. mRNA expression was increased for tumor necrosis factor(TNF)-α, interferon(IFN)-γ, interleukin (IL)-6, and decreased that for IL-10 in the colon of DSS colitis. In contrast, tranilast markedly decreased expression of mRNAs for the proinflammatory cytokines, and increased that of the anti-inflammatory cytokines. Moreover, tranilast increased HO-1 expression on colonic epithelial cells as well as on colon infiltrating cells of DSS colitis. CONCLUSION: Tranilast ameliorated DSS colitis by regulating mast cell degranulation, decreasing inflammatory cytokines and increasing anti-inflammatory cytokines. Tranilast might exert these effects partly through enhanced HO-1 expression in the colon, suggesting a potential adjunctive therapy for IBD.