Deoxycholic acid induced changes in electrophysiological parameters and macromolecular permeability in murine small intestine with and without functional enteric nervous system plexuses.

BACKGROUND: We have previously shown in mice that the fecal proportion and concentration of the hydrophobic bile acid deoxycholic acid (DCA) is elevated with high-fat feeding and that these changes are able to disrupt the intestinal barrier function. The aim of this study was to investigate whether these changes are mediated by the enteric nervous system (ENS). METHODS: The function of the ENS in the small intestinal tissues of mice was compromised by two different methods: by removing the seromuscular layer and by incubating the intact tissues with tetrodotoxin (TTX), a neural conduction blocker, before DCA treatment. Tissues with or without functional plexuses were mounted into a Ussing chamber system and treated with 3 mM DCA for 20 min. After DCA treatment, the intestinal permeability to fluorescein was assessed. Short-circuit current (Isc ) and transepithelial resistance (TER) were recorded throughout the experiment. KEY RESULTS: DCA increased intestinal fluorescein permeability only in tissues where the seromuscular layer was removed. In tissues with intact seromuscular layer, DCA induced a significant increase in TER, which was attenuated by blocking of the neural function by TTX. CONCLUSIONS & INFERENCES: The results of this study suggest that the DCA-induced increase observed in fluorescein permeability is not mediated through neural pathways, but more due to a direct effect on the epithelium. However, as TTX was able to attenuate the DCA-induced increase in TER, it can be speculated that DCA is also able to elicit responses through neural pathways.

Prophylactic potential of montelukast against mild colitis induced by dextran sulphate sodium in rats.

Cysteinyl leukotrienes play a part in inflammatory processes such as inflammatory bowel diseases. The present study aimed to evaluate the effects of the cys-LT-1 receptor antagonist montelukast on a mild colitis model in rats. Colitis was induced by administrating 4% dextran sulphate sodium (DSS, MW 45,000) in drinking water for 9 days. Montelukast (10 mg/kg/day) or vehicle was given by gastric gavage once daily simultaneously with DSS administration. A healthy control group receiving water as drinking fluid and vehicle by gastric gavage was included. Body weight loss, consistency of faeces (loose/diarrhoea) and occult blood in the faeces/ gross bleeding were assessed on days 6 - 9. After sacrifice, the following were assessed: colonic histology, the expression of inducible nitric oxide synthase, macrophage/monocyte marker ED1, cyclooxygenase-1 and cyclooxygenase-2, as well as the production of leukotriene B(4) and E(4), prostaglandin E(2), its metabolite bicyclic-prostaglandin E(2) and thromboxane B(2) in the colonic tissue incubation in vitro. Rats receiving DSS exhibited bloody diarrhoea from day 6 onwards. Montelukast significantly reduced the occult blood in the faeces/ gross bleeding, maintained normal body weight gain and tended to decrease the ratio of leukotriene B(4)/ prostaglandin E(2) production in the colon in vitro. The results indicate that montelukast has some potential to ameliorate mild experimental colitis induced by DSS.

Galacto-oligosaccharides stimulate the growth of bifidobacteria but fail to attenuate inflammation in experimental colitis in rats.

BACKGROUND: Galacto-oligosaccharides potentially attenuate colonic inflammation by two mechanisms: through beneficial effects on intestinal microflora and by increasing the colonic short-chain fatty acid concentration. The purpose of this study was to investigate the effects of galacto-oligosaccharides on the development of inflammation and on the growth of bifidobacteria in trinitrobenzene sulphonic acid (TNBS)-induced colitis, a model that has been shown to benefit from short-chain fatty acid administration and to be associated with alterations in the colonic microflora. METHODS: Rats were given daily either whey-derived or lactose-derived galacto-oligosaccharides (4 g kg(-1) day(-1), p.o.); starting 10 days before colitis induction, or dexamethasone (2 mg kg(-1) day(-1), s.c., a positive control), starting at colitis induction. Colon wet weight, macroscopic damage and myeloperoxidase activity were assessed 72 h after the induction of colitis. Faecal bifidobacteria were counted at the beginning of the study, and immediately before and 72 h after colitis induction. RESULTS: Galacto-oligosaccharides increased the colonic levels of bifidobacteria but also the levels of other bacterial species. Neither whey-derived nor lactose-derived galacto-oligosaccharides reduced the severity of inflammation. CONCLUSIONS: Galacto-oligosaccharides are able to modify gut microflora in severe TNBS-induced colitis, but unable to attenuate the inflammation.

Increased enterocyte production in gnotobiotic rats mono-associated with Lactobacillus rhamnosus GG.

There is increasing scientific and commercial interest in using beneficial microorganisms (i.e., probiotics) to enhance intestinal health. Of the numerous microbial strains examined, Lactobacillus rhamnosus GG has been most extensively studied. Daily intake of L. rhamnosus GG shortens the course of rotavirus infection by mechanisms that have not been fully elucidated. Comparative studies with germfree and conventional rats have shown that the microbial status of an animal influences the intestinal cell kinetics and morphology. The present study was undertaken to study whether establishment of L. rhamnosus GG as a mono-associate in germfree rats influences intestinal cell kinetics and morphology. L. rhamnosus GG was easily established in germfree rats. After 3 days of mono-association, the rate of mitoses in the upper part of the small intestine (jejunum 1) increased as much as 14 and 22% compared to the rates in germfree and conventional counterparts, respectively. The most striking alteration in morphology was an increase in the number of cells in the villi. We hypothesis that the compartmentalized effects of L. rhamnosus GG may represent a reparative event for the mucosa.

Acute effects of the cys-leukotriene-1 receptor antagonist, montelukast, on experimental colitis in rats.

Cysteinyl leukotrienes play a part in inflammatory reactions such as inflammatory bowel diseases. The aim of the present study was to evaluate the acute effects of a cys-leukotriene-1 receptor antagonist, montelukast, on trinitrobenzene sulphonic acid (TNBS)-induced colitis in rats. Montelukast (5, 10 or 20 mg kg(-1) day(-1)), a 5-lipoxygenase inhibitor, zileuton (50 or 100 mg kg(-1) day(-1), a positive control), or the vehicle was administered intracolonically to the rats twice daily throughout the study, starting 12 h before the induction of colitis with TNBS. The severity of colitis (macroscopic and histological assessment, as well as myeloperoxidase activity), the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2, and eicosanoid production in colonic tissue incubation were assessed 24 and 72 h after colitis induction. Montelukast increased prostaglandin E(2) production at 24 h and tended to reduce the cyclooxygenase-2 protein expression at 72 h, but did not influence the severity of colitis. Zileuton failed to decrease the inflammatory reaction in spite of reduced leukotriene B(4) production at 72 h. The results suggest that drugs that block cysteinyl leukotriene receptors have limited potential to ameliorate acute TNBS-induced colitis, but that they exert some beneficial effects which make them capable of modulating the course of colitis.

Effects of Lactobacillus rhamnosus GG and Lactobacillus reuteri R2LC on acetic acid-induced colitis in rats.

BACKGROUND: Certain lactobacilli reduce the severity of experimental colitis. The aim of this study was to compare the effects of a human strain Lactobacillus rhamnosus GG and a rat strain Lactobacillus reuteri R2LC on acetic acid-induced colitis in rats. METHODS: Lactobacillus rhamnosus GG, Lactobacillus reuteri R2LC or sulphasalazine were given orally to the rats. Colitis was assessed 72 h after induction with acetic acid. RESULTS: Lactobacillus reuteri R2LC significantly antagonized body weight loss caused by inflammation compared with Lactobacillus rhamnosus GG and sulphasalazine, and oedema formation in the colon compared with sulphasalazine. Lactobacillus reuteri R2LC reduced the median value of macroscopic ulceration and the protein content of inducible nitric oxide synthase by 50% and the median of the protein content of inducible cyclooxygenase by 30% compared with that of the colitis control group, and Lactobacillus rhamnosus GG reduced the median of inducible nitric oxide protein content by 40% and increased the median of inducible cyclooxygenase protein content by 30% compared with the median value of the colitis control group, but these differences were not statistically significant. CONCLUSIONS: The rat strain Lactobacillus reuteri R2LC, but not the human strain Lactobacillus rhamnosus GG, is of benefit in reducing the severity of acetic acid-induced colitis in rats. These results suggest that it is not the total amount of Lactobacillus but the particular species or strain of Lactobacillus that is important in attenuating experimental colitis.

The effect of chronic treatment with peripheral benzodiazepine receptor ligands on behavior and GABAA/benzodiazepine receptors in rat.

Rats were twice daily (2 x 10 mg/kg, i.p.) treated for three weeks with the peripheral benzodiazepine (BZ) receptor ligands Ro 5-4864 (4'-chlorodiazepam) and PK 11,195 (1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carbox ami de). After the first injection there were no differences between the drug-treated and control animals in behavioral tests. After 10 days treatment, the number of sniffings was increased in Ro 5-4864-treated rats. After the last injection, sniffings and ambulations were decreased in PK 11,195-treated animals. The number of rearings and groomings remained unchanged throughout the treatment, and there were no changes in the results in the elevated plus-maze test. Apparently these compounds are devoid of anxiolytic and anxiogenic effects at moderate doses. The effect of 72 a h withdrawal from the above mentioned chronic treatment on peripheral and central BZ receptors as well as on GABAA receptors was studied with receptor binding techniques using 3H-Ro 5-4864, 3H-flumazenil and 3H-muscimol, respectively, as ligands. The number of GABAA and central BZ receptors was lower after Ro 5-4864 treatment, as was the effect of progesterone-induced stimulation of 3H-muscimol binding. The number of peripheral BZ receptors was decreased after Ro 5-4864 and PK 11,195 treatments in the olfactory bulb but not in the cerebral cortex. The chronic treatment with peripheral BZ receptor ligands Ro 5-4864 and PK 11,195 produced only little behavioral effects. Ro 5-4864, often presented as an agonist of peripheral BZ receptors, was behaviorally inactive.(ABSTRACT TRUNCATED AT 250 WORDS)