endothelin-1 and Colitis

Bile acids (BAs) and BA receptors, including G protein-coupled bile acid receptor 1 (GPBAR1), represent novel targets for the treatment of metabolic and inflammatory disorders. However, BAs elicit myriad effects on cardiovascular function, although this has not been specifically ascribed to GPBAR1. This study was designed to test whether stimulation of GPBAR1 elicits effects on cardiovascular function that are mechanism based that can be identified in acute ex vivo and in vivo cardiovascular models, to delineate whether effects were due to pathways known to be modulated by BAs, and to establish whether a therapeutic window between in vivo cardiovascular liabilities and on-target efficacy could be defined. The results demonstrated that the infusion of three structurally diverse and selective GPBAR1 agonists produced marked reductions in vascular tone and blood pressure in dog, but not in rat, as well as reflex tachycardia and a positive inotropic response, effects that manifested in an enhanced cardiac output. Changes in cardiovascular function were unrelated to modulation of the levothyroxine/thyroxine axis and were nitric oxide independent. A direct effect on vascular tone was confirmed in dog isolated vascular rings, whereby concentration-dependent decreases in tension that were tightly correlated with reductions in vascular tone observed in vivo and were blocked by iberiotoxin. Compound concentrations in which cardiovascular effects occurred, both ex vivo and in vivo, could not be separated from those necessary for modulation of GPBAR1-mediated efficacy, resulting in project termination. These results are the first to clearly demonstrate direct and potent peripheral arterial vasodilation due to GPBAR1 stimulation in vivo through activation of large conductance Ca(2+) activated potassium channel K(Ca)1.1.

Topics: Animals; Arteries; Atrial Natriuretic Factor; CHO Cells; Colitis; Cricetinae; Cricetulus; Cyclic AMP; Cytokines; Dinitrofluorobenzene; Dogs; Endothelin-1; Humans; Imidazoles; In Vitro Techniques; Male; Nitric Oxide; Pyrimidines; Rats; Rats, Sprague-Dawley; Rats, Wistar; Receptors, G-Protein-Coupled; Thyroxine; Triazoles; Vasodilation

Ingestion by mice of dextran sodium sulfate (DSS) induces colonic vasoconstriction and inflammation, with some of the effects potentially mediated by the vasoconstrictor endothelin-1 (ET-1).. In this study, mice given 5% 40 kD DSS for 5-6 days had elevated colonic immunostaining for ET-1 and platelet endothelial cell adhesion molecule-1 (PECAM-1). Increased ET-1 can induce microvascular constriction; however, the increase in PECAM-1 is consistent with angiogenesis that could decrease flow resistance.. Our measurements of intestinal blood flow, via infused microspheres, suggests that these 2 factors may offset each other, with only a nonsignificant tendency for a DSS-induced decrease in flow. Daily administration of the endothelin converting enzyme inhibitor SM-19712 (15 mg/kg) attenuated DSS-induced increases in colonic immunostaining of ET-1 and PECAM-1.. SM-19712 attenuated histologic signs of tissue injury and inflammation induced by DSS, and decreased the extent of loose stools and fecal blood. However, the inhibitor did not significantly decrease DSS-induced colon shortening or tissue levels of myeloperoxidase (an indicator of neutrophil infiltration).

Topics: Animals; Aspartic Acid Endopeptidases; Blood Pressure; Body Weight; Colitis; Colon; Dextran Sulfate; Disease Models, Animal; Endothelin-1; Endothelin-Converting Enzymes; Enzyme Inhibitors; Ileum; Metalloendopeptidases; Mice; Mice, Inbred C57BL; Organ Size; Peroxidase; Platelet Endothelial Cell Adhesion Molecule-1; Sulfonamides; Sulfonylurea Compounds; Vasoconstriction

Endothelin (ET)-2, an ET family peptide, is highly expressed in intestine. However, the specific distribution and function of ET-2 remain unknown. We elucidated the expression profile and localization of ET-2 in mouse gastrointestinal tract. Real-time PCR analysis revealed that ET-2 gene expression in the gastrointestinal tract of healthy animals was relatively high in the colon. Immunohistochemical analysis revealed ET-2-like immunoreactivity mainly in epithelial cells of the mucosa throughout the intestinal tract of healthy animals. Intracellularly, ET-2 was concentrated close to the basement membrane of intestinal epithelial cells. A weak ET-2-like immunoreactivity was also localized to some neurofibers and the myenteric plexus of the muscle layer, coexpressing with vasoactive intestinal peptide. ET-2-like immunoreactivity was also detected at Brunner's glands of the duodenum and follicle-associated epithelium of Peyer's patch. In contrast, ET-1-like immunoreactivity was uniformly distributed in epithelial cells. In dextran sulfate sodium (DSS)-induced colitis, colonic ET-2 was upregulated during the late stage of DSS treatment. These results suggest that in intestinal epithelial cells ET-2 could be secreted into the lamina propria and the dome region in Peyer's patch, and that it might modulate immune cells in these sites for mucosal defense.

Topics: Animals; Colitis; Dextran Sulfate; Endothelin-1; Endothelin-2; Gene Expression Profiling; Humans; Immunohistochemistry; In Situ Hybridization; Indicators and Reagents; Intestinal Mucosa; Intestines; Male; Mice; Polymerase Chain Reaction; Protein Isoforms; Up-Regulation; Vasoactive Intestinal Peptide

The work shows that patients with chronic colitis have an expressed endothelial dysfunction, which becomes apparent as an increase of the level of vasoconstrictor endothelin-1 and decrease of the level of vasodilator nitric oxide. The obtained data indicate the role of the endothelial dysfunction in the pathogenesis of chronic colitis. The efficiency of the complex therapy with the use of folic acid and zinkteral for the restoration of the endothelium function is marked in comparison with the group of the patients treated with the help of the basic therapy.

Topics: Adult; Chronic Disease; Colitis; Endothelin-1; Endothelium, Vascular; Female; Folic Acid; Humans; Male; Middle Aged; Nitric Oxide; Zinc Sulfate

There have been suggestions that endothelins (ET-1, ET-2, ET-3) are involved in the pathogenesis of human inflammatory bowel disease (IBD). Furthermore, the non-selective endothelin receptor antagonist, bosentan, ameliorates colonic inflammation in TNBS colitis in rats. However, no studies have measured the tissue expression and release of endothelins in human IBD in direct comparison to experimental TNBS colitis. Mucosal biopsies were obtained from 114 patients (42 Crohn's colitis, 35 ulcerative colitis and 37 normal) and compared to whole colonic segments from rats with TNBS colitis. ET-1/2 levels were reduced in human IBD but greatly increased in experimental TNBS colitis. RT-PCR indicated ET-2 was the predominant endothelin isoform in human IBD whereas ET-1 prevailed in the TNBS model. No associations were found between human IBD and tissue expression, content or release of ET-1/2. Our study shows, therefore, that unlike TNBS colitis in rats, in which ET-1/2 levels are greatly elevated and ET receptor antagonists are efficacious, there is no significant link between endothelins and human IBD.

Topics: Animals; Colitis; Dinoprostone; Endothelin-1; Endothelin-2; Endothelins; Humans; Inflammatory Bowel Diseases; Intestinal Mucosa; L-Lactate Dehydrogenase; Male; Peroxidase; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; Trinitrobenzenesulfonic Acid; Tumor Necrosis Factor-alpha

Shiga toxin, produced by Escherichia coli O157:H7, is important for the pathogenicity of the epidemic form of hemolytic uremic syndrome (HUS). This toxin has recently been found to stimulate endothelin-1 synthesis in cultured endothelial cells in vitro.. We investigated endothelin and cytokine levels in sera during a large outbreak of E. coli O157:H7 infection in Osaka, Japan, in 1996. Eleven patients with HUS and 9 patients with hemorrhagic colitis at the onset of E. coli O157:H7 infection were studied.. Serum IL-6 (p < 0.01), IL-8 (p < 0.05), IL-10 (p < 0.001) and endothelin (p < 0.001) levels were significantly increased in patients with HUS compared to those with colitis only. The serum thrombomodulin level, a molecular marker of endothelial damage, also showed a significant positive correlation with serum IL-6 (p < 0.01), IL-8 (p < 0.01), IL-10 (p < 0.01) and endothelin (p < 0.001) levels. In a HUS patient, the increase in serum IL-10 and endothelin levels reached a plateau prior to the peak of serum creatinine levels.. Increased serum endothelin synthesis by Shiga toxin in vivo was proven in HUS secondary to E. coli O157:H7 infection. Increased serum endothelin and IL-10 levels were speculated to be associated with the development of HUS through vascular endothelial damage caused by E. coli O157:H7 infection.

Topics: Case-Control Studies; Colitis; Creatinine; Disease Outbreaks; Endothelin-1; Escherichia coli Infections; Escherichia coli O157; Female; Gastrointestinal Hemorrhage; Hemolytic-Uremic Syndrome; Humans; Interleukin-10; Interleukin-6; Interleukin-8; Japan; Male; Thrombomodulin; Time Factors