BackgroundInflammatory bowel diseases (IBD), including mainly ulcerative colitis (UC) and Crohn's disease (CD), are inflammatory disorders of the gastrointestinal tract caused by an interplay of genetic and environmental factors. Murine colitis model induced by Dextran Sulfate Sodium (DSS) is an animal model of IBD that is commonly used to address the pathogenesis of IBD as well as to test efficacy of therapies. In this study we systematically analyzed clinical parameters, histological changes, intestinal barrier properties and cytokine profile during the colitic and recovery phase.MethodsC57BL/6 mice were administered with 3.5% of DSS in drinking water for various times. Clinical and histological features were determined using standard criteria. Myeloperoxidase (MPO) activity, transepithelial permeability and proinflammatory mediators were determined in whole colon or proximal and distal parts of colon.ResultsAs expected after administration of DSS, mice manifest loss of body weight, shortening of colon length and bloody feces. Histological manifestations included shortening and loss of crypts, infiltration of lymphocytes and neutrophil, symptoms attenuated after DSS withdrawal. The MPO value, as inflammation indicator, also increases significantly at all periods of DSS treatment, and even after DSS withdrawal, it still held at very high levels. Trans-mucosal permeability increased during DSS treatment, but recovered to almost control level after DSS withdrawal. The production of proinflammatory mediators by colonic mucosa were enhanced during DSS treatment, and then recovered to pre-treated level after DSS withdrawal. Finally, enhanced expression of proinflammatory mediators also revealed a different profile feature in proximal and distal parts of the colon.ConclusionExperimental colitis induced by DSS is a good animal model to study the mechanisms underlying the pathogenesis and intervention against IBD, especially UC.
Background and significance-The A 2B adenosine receptor (A 2B AR) is the predominant adenosine receptor expressed in the colonic epithelia. We have previously shown that A 2B AR mRNA and protein levels are upregulated during colitis. In this study we addressed the role of the A 2B AR in the development of murine colitis and potential mechanism underlying its effects.
Adenosine is an endogenous signaling molecule upregulated during inflammatory conditions. Acting through the A2b receptor (A2bR), the predominant adenosine receptor in human colonic epithelia, adenosine has been directly implicated in immune and inflammatory responses in the intestine. Little is known about expression and regulation of A2bR during inflammation. Tumor necrosis factor alpha (TNF-alpha) is highly upregulated during chronic and acute inflammatory diseases. This study examined the expression of A2bR during colitis and studied effects of TNF-alpha on A2bR expression, signaling and function. Results demonstrated that A2bR expression increases during active colitis. TNF-alpha pretreatment of intestinal epithelial cells increased A2bR messenger RNA and protein expression. TNF-alpha significantly increased adenosine-induced membrane recruitment of A2bR and cyclic adenosine monophosphate downstream signaling. Further, TNF-alpha potentiated adenosine-induced shortcircuit current and fibronectin secretion. In conclusion, we demonstrated that TNF-alpha is an important regulator of A2bR, and during inflammation, upregulation of TNF-alpha may potentiate adenosine-mediated responses.
Background and purpose: The adenosine 2B (A 2B ) receptor is the predominant adenosine receptor expressed in the colon. Acting through the A 2B receptor, adenosine mediates chloride secretion, as well as fibronectin and interleukin (IL)-6 synthesis and secretion in intestinal epithelial cells. A 2B receptor mRNA and protein expression are increased during human and murine colitis. However, the effect of the A 2B receptor in the activation of the intestinal inflammatory response is not known. In this study, we examined the effect of A 2B receptor antagonism on murine colitis. Experimental approach: Dextran sodium sulphate (DSS)-treated mice and piroxicam-treated IL-10 À/À mice were used as animal models of colitis. The A 2B receptor-selective antagonist, ATL-801, was given in the diet. Key results: Mice fed ATL-801 along with DSS showed a significantly lower extent and severity of colitis than mice treated with DSS alone, as shown by reduced clinical symptoms, histological scores, IL-6 levels and proliferation indices. The administration of ATL-801 prevented weight loss, suppressed the inflammatory infiltrate into colonic mucosa and decreased epithelial hyperplasia in piroxicam-treated IL-10 À/À mice. IL-6 and keratinocyte-derived chemokine (KC) concentrations in the supernatants of colonic organ cultures from colitic mice were significantly reduced by ATL-801 administration. Conclusions and implications: Taken together, these data demonstrate that the intestinal epithelial A 2B receptor is an important mediator of pro-inflammatory responses in the intestine and that A 2B receptor blockade may be an effective therapeutic strategy to treat inflammatory bowel disease.
Activation of TLR3 on cells that are accessible by systemic, but not oral, administration of synthetic viral RNA results in protection against the acute inflammation that can ensue upon damage of the gut epithelium. Thus, this viral RNA analog, which is under clinical trials for other inflammatory disorders (e.g., lupus), may also have therapeutic value for inflammatory bowel disease.
Purinergic receptors comprise a family of transmembrane receptors that are activated by extracellular nucleosides and nucleotides. The two major classes of purinergic receptors, P1 and P2, are expressed widely in the gastrointestinal tract as well as immune cells. The purinergic receptors serve a variety of functions from acting as neurotransmitters, to autocoid and paracrine signaling, to cell activation and immune response. Nucleosides and nucleotide agonist of purinergic receptors are released by many cell types in response to specific physiological signals, and their levels are increased during inflammation. In the past decade, the advent of genetic knockout mice and the development of highly potent and selective agonists and antagonists for the purinergic receptors have significantly advanced the understanding of purinergic receptor signaling in health and inflammation. In fact, agonist/antagonists of purinergic receptors are emerging as therapeutic modalities to treat intestinal inflammation. In this article, the distribution of the purinergic receptors in the gastrointestinal tract and their physiological and pathophysiological role in intestinal inflammation will be reviewed.
BackgroundNeurogenic inflammation plays a major role in the pathogenesis of inflammatory bowel disease (IBD). We examined the role of neuropeptide Y (NPY) and neuronal nitric oxide synthase (nNOS) in modulating colitis.MethodsColitis was induced by administration of dextran sodium sulphate (3% DSS) or streptomycin pre-treated Salmonella typhimurium (S.T.) in wild type (WT) and NPY (NPY−/−) knockout mice. Colitis was assessed by clinical score, histological score and myeloperoxidase activity. NPY and nNOS expression was assessed by immunostaining. Oxidative stress was assessed by measuring catalase activity, glutathione and nitrite levels. Colonic motility was assessed by isometric muscle recording in WT and DSS-treated mice.ResultsDSS/S.T. induced an increase in enteric neuronal NPY and nNOS expression in WT mice. WT mice were more susceptible to inflammation compared to NPY−/− as indicated by higher clinical & histological scores, and myeloperoxidase (MPO) activity (p<0.01). DSS-WT mice had increased nitrite, decreased glutathione (GSH) levels and increased catalase activity indicating more oxidative stress. The lower histological scores, MPO and chemokine KC in S.T.-treated nNOS−/− and NPY−/−/nNOS−/− mice supported the finding that loss of NPY-induced nNOS attenuated inflammation. The inflammation resulted in chronic impairment of colonic motility in DSS-WT mice. NPY –treated rat enteric neurons in vitro exhibited increased nitrite and TNF-α production.ConclusionsNPY mediated increase in nNOS is a determinant of oxidative stress and subsequent inflammation. Our study highlights the role of neuronal NPY and nNOS as mediators of inflammatory processes in IBD.
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