Cory M. Hogaboam

Tapeworm infection reduces epithelial ion transport abnormalities in murine dextran sulfate sodium-induced colitis

ABSTRACT The rat tapeworm Hymenolepis diminuta was used to test the hypothesis that helminth infection could modulate murine colitis. Mice were infected with five H. diminutacysticercoids, and colitis was evoked via free access to 4% (wt/vol) dextran sulfate sodium (DSS)-containing drinking water for 5 days. BALB/c mice were either infected with H. diminuta and 7 days later exposed to DSS (prophylactic strategy) or started on DSS and infected with H. diminuta 48 h later (treatment strategy). Naive andH. diminuta-only-infected mice served as controls. On autopsy, colonic segments were processed for histological examination and myeloperoxidase (MPO) measurement or mounted in Ussing chambers for assessment of epithelial ion transport. Cytokines (gamma interferon [IFN-γ], interleukin 12 [IL-12], and IL-10) were measured in serum and colonic tissue homogenates. DSS treatment resulted in reduced ion responses (indicated by short-circuit current [Isc]) to electrical nerve stimulation, the cholinergic agonist carbachol, and the adenylate cyclase activator forskolin compared to controls. H. diminuta infection, either prophylactic or therapeutic, caused a significant (P < 0.05) amelioration of these DSS-induced irregularities in stimulated ion transport. In contrast, the histopathology (i.e., mixed immune cell infiltrate, edema, and ulcerative damage) and elevated MPO levels that accompany DSS colitis were unaffected by concomitant H. diminuta infection. Similarly, there were no significant differences in levels of IFN-γ, IL-12, or IL-10 in serum or tissue from any of the treatment groups at the time of autopsy. We suggest that abolishment of colitis-induced epithelial ion transport abnormalities by H. diminuta infection provides proof-of-principle data and speculate that helminth therapy may provide relief of disease symptoms in colitis.

An orally active non-selective endothelin receptor antagonist, bosentan, markedly reduces injury in a rat model of colitis

Activation of endothelial cells by vasoactive mediators, such as endothelins, may be an early, strategically important step in the initiation of inflammation in the intestine. In view of recent evidence that inflammatory bowel disease is associated with elevated intestinal concentrations of endothelins and upregulated expression of endothelin receptors on vascular endothelium in intestine, endothelins may become therapeutic targets in inflammatory bowel disease. The recent availability of an orally active, mixed endothelin receptor antagonist, bosentan, allowed us to examine the role of endothelins in a rat model of colitis. Colitis was induced by intra-rectal administration of trinitrobenzene sulphonic acid. In each treatment group, rats were treated with bosentan (10-60 mg/kg p.o.) 24 and 2 h prior to (pre-dose) or 1 h after the induction (post-induction) of colitis and all animals were treated every 24 h thereafter for 5 days. On day 6, stool consistency and the presence of adhesions in the peritoneal cavity were accessed. Colonic tissue samples were removed for determination of macroscopic and microscopic tissue injury, and myeloperoxidase activity. Colitis was typified by tissue ulceration in the distal colon and a corresponding 35-fold increase in myeloperoxidase activity compared to non-inflamed controls. Daily treatment with bosentan dose-dependently reduced colonic damage and myeloperoxidase activity when bosentan was given prior to induction of colitis. In the pre-dose group, the greatest beneficial effect of bosentan was observed at 60 mg/kg; colonic damage and granulocyte infiltration were attenuated by > 80%. A partial therapeutic effect of bosentan was also observed at 60 mg/kg when the pre-treatment regimen was excluded. These findings demonstrate that an orally active, mixed endothelin receptor antagonist has marked protective and therapeutic effects in an animal model of colitis.

Therapeutic effects of the endothelin receptor antagonist Ro 48-5695 in the TNBS/DNBS rat model of colitis.

Objective Endothelins can act as polyfunctional cytokines. It is therefore possible that endothelins could play an active role in gut inflammation. Elevated levels of endothelin‐1 have been reported in ulcerative colitis and Crohns disease. The aim of this study was to establish the therapeutic effect of a ‘new’ endothelin receptor antagonist Ro 48‐5695 in an animal model of inflammatory bowel disease. This study compares the effect of Ro 48‐5695 on colonic damage induced by two haptens: trinitrobenzenesulphonic (TNBS) or dinitrobenzenesulphonic acid (DNBS). Methods Colitis was induced by intra‐rectal administration of TNBS or DNBS. After TNBS/DNBS injury, rats were treated with 10.0, 3.0, 1.0 or 0.3 mg/kg of Ro 48‐5695 orally, daily for 5 days. On day 6 post‐hapten treatment, colonic tissues were removed and examined in a blinded fashion for macroscopic damage (damage score) and myeloperoxidase (MPO) activity. Stool consistency and adhesions were also measured. Results Oral administration of Ro 48‐5695 almost completely prevented TNBS‐induced damage at a dose of 10 mg/kg. The same dose in this model also had a therapeutic effect as measured by MPO and incidence of diarrhoea and adhesions. In DNBS‐induced colonic damage, Ro 48‐5695 was more potent and at 1.0 and 3.0 mg/kg decreased the damage score by 50 and 60% respectively; also the incidence of adhesions and diarrhoea was significantly reduced. However, MPO activity in this model was affected only by the highest dose of Ro 48‐5695 tested (3.0 mg/kg) where it was reduced by 48%. Conclusions These data provide evidence for the involvement of endothelins in the pathophysiology of inflammatory bowel disease and support the possibility of exploring a new therapeutic approach. Eur J Gastroenterol Hepatol 12:257‐265

Neuromuscular regulation of T-cell activation

Recent investigations in our laboratory have shown that murine intestinal smooth muscle cells (ISMCs) can exert an immunomodulatory effect on T-cells. Therefore, we examined the effects of substance P, calcitonin gene-related peptide (CGRP) and vasoactive intestinal peptide (VIP) on the ability of ISMCs to modulate T-cell proliferation and lymphokine generation. T-cell proliferation was observed when these cells were co-cultured with IFN-pretreated C57/BL6 ISMCs which expressed major histocompatibility complex II (MHC II), but not during T-cell co-culture with C2D (MHC II -/-) ISMCs pretreated in the same manner. T-cell proliferation during co-culture with C57/BL6 ISMCs was also associated with significantly enhanced T-cell synthesis of IFN. When CGRP (at 10(-9) M), but not substance P or VIP, was added to C57/BL6 ISMCs during the IFN-pretreatment period. T-cell proliferation was significantly increased. However, increased T-cell proliferation was not observed if the concentration of CGRP was increased to 10(-6) M. At the higher concentration, addition of substance P or VIP during the pretreatment period significantly inhibited the subsequent T-cell proliferation. Pretreatment of C57/BL6 ISMCs with any of the three neuropeptides and IFN resulted in the diminished production of IL-4 and IFN by co-cultured T-cells. A similar pattern of cytokine secretion was observed during T-cell co-culture with IFN- and neuropeptide-pretreated C2D ISMCs except when 10(-6) M substance P was added; IFN secretion by co-cultured T-cells was increased 4-fold under these conditions. Taken together, these data show a direct modulatory role for neuropeptides in the interaction between ISMCs and T-cells and suggest that, in general, neuropeptides may dampen immune responses in the neuromuscular layers of the inflamed intestine.

Role of smooth muscle in intestinal inflammation

The observation that active ulcerative colitis is accompanied by a reduction in motor activity in the distal colon1–3 suggests that the contractility of colonic smooth muscle may be impaired as a result of inflammation. this has been confirmed in an in-vitro study of human colonic circular muscle in which contraction induced by either bethanechol or KC1 was significantly reduced in comparison to muscle obtained from patients without inflammatory bowel disease (IBD)4, suggesting that the underlying mechanism is located at the postreceptor level in the excitation—contraction coupling of the muscle cell. Similar observations have been made in animal models of colitis5. In our study5, a similar decrease in colonic smooth muscle contractility was observed in colitis induced by chemical injury (acetic acid or trinitrobenzene sulfonic acid, TNB), as well as infection (Trichinella spiralis) These results also illustrate that inflammation-induced changes in smooth muscle are nonspecific in that they do not appear to be influenced by the manner in which colitis is induced.