Participation of mast cells in colitis inflammation induced by dextran sulfate sodium

Mast Cells Exert Anti-Inflammatory Effects in an IL10-/- Model of Spontaneous Colitis

Mast cells are well established as divergent modulators of inflammation and immunosuppression, but their role in inflammatory bowel disease (IBD) remains to be fully defined. While previous studies have demonstrated a proinflammatory role for mast cells in acute models of chemical colitis, more recent investigations have shown that mast cell deficiency can exacerbate inflammation in spontaneous colitis models, thus suggesting a potential anti-inflammatory role of mast cells in IBD. Here, we tested the hypothesis that in chronic, spontaneous colitis, mast cells are protective. We compared colitis and intestinal barrier function in IL10^−/− mice to mast cell deficient/IL10^−/− (double knockout (DKO): Kit^Wsh/Wsh × IL10^−/−) mice. Compared with IL10^−/− mice, DKO mice exhibited more severe colitis as assessed by increased colitis scores, mucosal hypertrophy, intestinal permeability, and colonic cytokine production. PCR array analyses demonstrated enhanced expression of numerous cytokine and chemokine genes and downregulation of anti-inflammatory genes (e.g., Tgfb2, Bmp2, Bmp4, Bmp6, and Bmp7) in the colonic mucosa of DKO mice. Systemic reconstitution of DKO mice with bone marrow-derived mast cells resulted in significant amelioration of IL10^−/−-mediated colitis and intestinal barrier injury. Together, the results presented here demonstrate that mast cells exert anti-inflammatory properties in an established model of chronic, spontaneous IBD. Given the previously established proinflammatory role of mast cells in acute chemical colitis models, the present findings provide new insight into the divergent roles of mast cells in modulating inflammation during different stages of colitis. Further investigation of the mechanism of the anti-inflammatory role of the mast cells may elucidate novel therapies.

Augmented activity of the pelvic nerve afferent mediated by TRP channels in dextran sulfate sodium (DSS)-induced colitis of rats

Enteritis has been recognized as a major symptom in domestic animals and human patients suffering from feed and food poisonings. The aim of the present study was to clarify the excitatory mechanism of the pelvic nerve afferent which may influence the occurrence of enteritis in response to nociceptive chemical stimuli of the colon in normal and abnormal rats with colitis induced by dextran sulfate sodium (DSS). The pelvic nerve afferent activity was markedly increased by colonic instillation of solution (0.5 ml) of acetic acid (5-25%) and capsaicin (100 μg/ml). The nerve activity was augmented by colonic instillation of capsaicin to a greater extent in rats with DSS-induced colitis than in normal control rats. This augmented activity by capsaicin was more prominent at one day (DSS-1) than at 8 day (DSS-8) after the administration of DSS. The increased nerve activity caused by capsaicin in DSS-1 and DSS-8 was significantly inhibited by pretreatment with ruthenium red, which is a nonselective inhibitor of TRP channels of unmyelinated C-fibers (nociceptors). In conclusion, it was elucidated that the nociceptive function of the pelvic nerve was largely elevated at one day after DSS-induced colitis and such increased function was mostly mediated by TRP channels.

Factors influencing the development of animal models of dextran sulphate sodium-induced colitis

The animal models of dextran sulphate sodium (DSS)-induced colitis have demonstrated several correlations with human ulcerative colitis (UC) since the first report of DSS-induced colitis in hamsters in 1985. These animal models have similarities to human UC in etiology, pathology, pathogenesis and therapeutic response, and are deemed suitable for investigating the pathogenesis and therapeutic options of UC and UC-related dysplasia-adenocarcinoma sequence. Although induction of colitis with DSS is relatively cheap and simple, the development of this model is influenced by many factors, such as DSS concentration, administration duration, DSS molecular weight and animal species. These factors are important for successful development of DSS-induced colitis. In this paper we summarize factors influencing the development of animal models of DSS-induced colitis.

Intestinal mast cells in gut inflammation and motility disturbances

Mast cells may be regarded as prototypes of innate immune cells that can be controlled by neuronal mediators. Their activation has been implicated in many types of neuro-inflammatory responses, and related disturbances of gut motility, via direct or indirect mechanisms that involve several mechanisms relevant to disease pathogenesis such as changes in epithelial barrier function or activation of adaptive or innate immune responses. Here we review the evidence for the involvement of mast cells in the inflammation of the bowel wall caused by bowel manipulation that leads to motility disturbances such as postoperative gastroparesis and ileus. Also in IBD there is substantial evidence for the involvement of mast cells and a mast cell-mediated neuroimmune interaction showing an increased number and an increased degranulation of mast cells. We discuss the potential of mast cell inhibition as a bona fide drug target to relief postoperative ileus. Further research on mast cell-related therapy either by stabilizing the mast cells or by blocking specific mast cell mediators as adjunctive therapy in IBD is encouraged, bearing in mind that several drugs currently used in the treatment of IBD possess properties affecting mast cell activities. This article is part of a Special Issue entitled: Mast cells in inflammation.

Rectal administration of tranilast ameliorated acute colitis in mice through increased expression of heme oxygenase-1

Mast cells play a key role in the pathophysiology of inflammatory bowel disease (IBD). Tranilast, a mast cell stabilizer, has been empirically used for IBD in Japan, but its precise role in the treatment of IBD is largely unknown. To investigate the role of tranilast for the treatment of IBD, tranilast was administered intrarectally to mice with dextran sulfate sodium (DSS)-induced colitis. Tranilast ameliorated DSS colitis clinically and pathologically, as demonstrated by decreased number and degranulation of mast cells in the colon. mRNA expression was increased for tumor necrosis factor-alpha, interferon-gamma and interleukin (IL)-6, and decreased for IL-10 in the colon of DSS colitis mice. In contrast, tranilast markedly decreased expression of mRNAs for the pro-inflammatory cytokines, and increased that of the anti-inflammatory cytokines. Moreover, tranilast increased heme oxygenase (HO)-1 expression on colonic epithelial cells as well as on colon-infiltrating cells of DSS colitis. In 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.

Role of chymase-dependent matrix metalloproteinase-9 activation in mice with dextran sodium sulfate-induced colitis

Matrix metalloproteinase (MMP)-9 plays an important role in the pathogenesis of colitis. Recent studies have demonstrated that chymase is involved in the conversion of promatrix metalloproteinase (proMMP)-9 to MMP-9. However, whether chymase contributes to the activation of proMMP-9 in colitis has remained unclear. In this study, we administered 5% dextran sodium sulfate (DSS) solution to mice for 7 days. At 7 days after starting administration, both chymase activity and MMP-9 activity were significantly increased. In extract from colitis in DSS-treated mice, MMP-9 activity was significantly increased after 8 h of incubation, but increased activity was almost completely suppressed in the presence of a chymase inhibitor, 2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[{3,4-dioxo-1-phenyl-7-(2-pyridyloxy)}-2-heptyl] acetamide (NK3201). At 7 days after starting administration, intestinal length was significantly shorter in DSS-treated mice than in normal mice, but these changes were significantly prevented by NK3201 (10 mg/kg per day i.p.). Disease activity index and histological damage score were also significantly reduced by NK3201. The filtrated neutrophil number was significantly decreased by NK3201. Furthermore, NK3201 significantly attenuated not only chymase activity but also MMP-9 activity in DSS-treated mice. These findings suggest that chymase plays an important role in the development of colitis via MMP-9 activation.

Mast cells and nerves tickle in the tummy: implications for inflammatory bowel disease and irritable bowel syndrome

Mast cells are well known as versatile cells capable of releasing and producing a variety of inflammatory mediators upon activation and are often found in close proximity of neurons. In addition, inflammation leads to local activation of neurons resulting in the release neuropeptides, which also play an important immune modulatory role by stimulation of immune cells. In intestinal disorders like inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), the number of mast cells is known to be much higher than in the normal intestine. Moreover, both these disorders are also reported to be associated with alterations in neuropeptide content and in neural innervation. Mutual association between mast cells and enteric nerves has been demonstrated to be increased in pathophysiological conditions and contribute to spreading and amplification of the response in IBD and IBS. In this review the focus lies on studies appointed to the direct interaction between mast cells and nerves in IBD, IBS, and animal models for these disorders so far.

Assessment of determinants of optimum performance of the CAST-2000 ELISA procedure

The Cellular Antigen Stimulation Test (CAST), a recent innovation in the laboratory detection of allergen sensitivity, is a functional assay based on the release of sulphidoleukotrienes (LTs) from allergen-activated circulating basophils. The current study was undertaken to establish optimum determinants of this procedure. The results demonstrate that treatment of blood with preservative-free heparin in polypropylene containers, and removal of erythrocytes by selective lysis with 0.83% ammonium chloride are excellent alternatives to the use of CAST venepuncture tubes and dextran, respectively. Similarly, decreasing and increasing the leucocyte concentration by 0.5- and 4-fold, respectively, as well as omission of interleukin-3 (IL-3) were also without significant effect. However, treatment of leucocyte suspensions with bacterial endotoxin (>1 microg/ml) activated the release of sulphidoleukotrienes from basophils and/or other types of leucocytes. The findings of this study are clearly relevant, both with respect to cost and performance, when implementing the CAST in clinical immunology laboratories.

Possible role of mucosal mast cells in the recovery process of colitis induced by dextran sulfate sodium in rats

To clarify the role of mucosal mast cells in the lesion sites of colitis induced by dextran sulfate sodium (DSS) in rats, we investigated the histological changes and alterations relevant to mucosal mast cells in the spontaneous recovery process of colitis. Oral administration of 4% DSS solution for 11 days resulted in surface epithelial loss, crypt loss and goblet cell depletion in the rectal mucosa. A marked infiltration of inflammatory cells into the mucosa, which was consistent with a significant increase in myeloperoxidase (MPO) activity, was observed. In addition, mucosal mast cell number and rat mast cell protease (RMCP) I and II levels in the rectum increased at day 0 after DSS treatment, and most of the mucosal mast cells were degranulated. After replacing 4% DSS solution with water, re-epithelialization and restoration of goblet cells were observed at day 5 and day 10, respectively, but crypt damage was hardly recovered even at day 20. The elevated myeloperoxidase activity was significantly decreased from day 5 after DSS treatment. The increased number of mucosal mast cells was further elevated up to about 1.5-fold at day 10 and day 20 after DSS treatment and little degranulation was observed. In the spontaneous recovery process, the increased rat mast cell protease II level in the rectum was maintained for 20 days, while the increased rat mast cell protease I level was gradually decreased and recovered to control level. These results suggest that proliferated mucosal mast cells remained for 20 days, although most of infiltrated inflammatory cells disappeared in spontaneous recovery process of colitis. It may therefore be presumed that proliferated mucosal mast cells play a role in spontaneous recovery process of the colitis induced by DSS.