The purpose of this study was to investigate the effect of lipopolysaccharide (LPS) on spontaneous contractions and acetylcholine (ACh) induced contractions of rabbit intestinal segments in vitro, with two different protocols: intestinal segments isolated from LPS-treated rabbits and intestinal segments incubated with LPS. The frequency of spontaneous movements decreased significantly in LPS-treated rabbits at 2 microg kg-1 in the duodenum and 20 microg kg-1 in the duodenum, jejunum and ileum. LPS (0.2 microg kg-1) reduced significantly the ACh contractions (10-6 mol L-1) in the duodenum (61%), jejunum (48%) and ileum (21%). Indomethacin (1, 5 and 10 mg kg-1) administered 15 min before LPS (0.2 microg kg-1) antagonized the LPS effects on the ACh-induced contractions. Prostaglandin (PG)E2 (8 microg kg-1) inhibited significantly the frequency of spontaneous contractions in the ileum and reduced the ACh-induced contractions in the three segments, mimicking the LPS effects. The amplitude and frequency of contractions in rabbit intestinal segments previously incubated with LPS (0.03, 0.3, 3 and 30 microg mL-1) were not modified with respect to the control. The ACh-induced contractions (10-4 mol L-1) were significantly reduced after 90 min of incubation with LPS. The inhibition of LPS (0.3 microg mL-1) was 43% in the duodenum, 35% in the jejunum and 17% in the ileum. Indomethacin added before LPS blocked the effect of LPS on the ACh-induced contractions in the duodenum, jejunum and ileum. These results show that LPS decreases intestinal contractility in rabbits and suggest that PGs are implicated in these actions.

Lipopolysaccharide decreases the duodenal contractility in rabbits and increases the production of free radicals. p38 MAPK is a mediator of these effects.

Jasonia glutinosa (L.) DC., known as rock tea (RT), is traditionally used in Spain as a digestive due to its beneficial properties in bowel disorders. The pharmacological nature of these properties has not been established yet. The aim of this work was to evaluate the therapeutic utility of RT in experimental colitis and to identify chemical constituents with anti-inflammatory and/or anti-oxidative properties. RT extract was prepared with ethanol in a Soxhlet apparatus and analysed by HPLC-DAD. Superoxide radical scavenging properties, xanthine oxidase and lipoxygenase (5-LOX) inhibitory activity, and capability to lower nitric oxide (NO) and tumour necrosis factor α (TNF-α) levels were measured in cellfree and cell-based assays. In the 2.5%-dextran-sodium sulphate (DSS) injury-repair model of ulcerative colitis (UC), mice were daily treated with sulfasalazine (SSZ, as reference drug, 100 mg/kg bw), RT (5, 25 and 50 mg/kg bw, p.o.), or vehicle over 20-days. Colitis was scored daily. Colon samples were macroscopically and histopathologically examined. Protein levels of myeloperoxidase (MPO), interleukins 6, and 10 (IL-6, IL-10), inducible NO synthase (iNOS), and cyclooxygenase-2 (COX-2) were studied as markers of oxidative stress and inflammatory activity. The integrity of the apical epithelial layer was assessed by immunofluorescence staining of zonula ocludens-1 (ZO-1). Finally, intestinal contractility was also evaluated by isometric myography. Fifteen phenolic compounds and three pigments were identified and quantified, of which caffeoylquinic acids, and the flavonoid, quercetin-3-O-galactoside, were the most abundant. RT extract significantly scavenged superoxide radicals, inhibited 5-LOX activity, and lowered NO and TNF-α levels. DSS-treated mice receiving RT scored clinically lower than controls during the first 3-days of DSS-treatment and during the recovery period. SSZ was less effective than RT. Anatomical and histological examination of colon samples revealed that RT significantly prevented shortening and thickening, and lowered the macroscopic damage score. RT also significantly prevented the increase of MPO activity, IL-6 levels, iNOS and COX-2 expression, the loss of ZO-1 apical expression, and normalized contractility disturbances. In conclusion, daily administration of RT showed therapeutic properties in the DSS-model of UC. The benefits of RT can likely be attributed to its anti-inflammatory and antioxidant phenolic and flavonoid constituents.

No abstract

Serotonin (5-HT) is an essential gastrointestinal modulator whose effects regulate the intestinal physiology. 5-HT effects depend on extracellular 5-HT bioavailability, which is controlled by the serotonin transporter (SERT) expressed in both the apical and basolateral membranes of enterocytes. SERT is a critical target for regulating 5-HT levels and consequently, modulating the intestinal physiology. The deregulation of innate immune receptors has been extensively studied in inflammatory bowel diseases (IBD), where an exacerbated defense response to commensal microbiota is observed. Interestingly, many innate immune receptors seem to affect the serotonergic system, demonstrating a new way in which microbiota could modulate the intestinal physiology. Therefore, our aim was to analyze the effects of NOD1 activation on SERT function, as well as NOD1's interaction with other immune receptors such as TLR2 and TLR4. Our results showed that NOD1 activation inhibits SERT activity and expression in Caco-2/TC7 cells through the extracellular signal-regulated kinase (ERK) signaling pathway. A negative feedback between 5-HT and NOD1 expression was also described. The results showed that TLR2 and TLR4 activation seems to regulate NOD1 expression in Caco-2/TC7 cells. To assess the extend of cross-talk between NOD1 and TLRs, NOD1 expression was measured in the intestinal tract (ileum and colon) of wild type mice and mice with individual knockouts of TLR2, and TLR4 as well as double knockout TLR2/TLR4 mice. Hence, we demonstrate that NOD1 acts on the serotonergic system decreasing SERT activity and molecular expression. Additionally, NOD1 expression seems to be modulated by 5-HT and other immune receptors as TLR2 and TLR4. This study could clarify the relation between both the intestinal serotonergic system and innate immune system, and their implications in intestinal inflammation.

Cytokines are involved in fever and other symptoms of the acute phase response induced by endotoxins. The aim of this work was to study the involvement of central tumour necrosis factor-alpha (TNF-alpha) in the changes induced by lipopolysaccharide (LPS) on gastrointestinal (GI) motility in sheep. Body temperature and myoelectric activity of the antrum, duodenum and jejunum was recorded continuously. Intravenous (i.v.) administration of LPS (0.1 micro g kg-1)-induced hyperthermia, decreased gastrointestinal myoelectric activity and increased the frequency of the migrating motor complex (MMC). These effects started 40-50 min after LPS and lasted for 6-7 h. TNF-alpha (50 and 100 ng kg-1) mimicked these effects when injected intracerebroventricularly (i.c.v.) but not i.v. Pretreatment with soluble recombinant TNF receptor (TNFR:Fc, 10 micro g kg-1, i.c.v.) abolished the TNF-induced actions and reduced those evoked by LPS. Furthermore, the effects induced by either LPS or TNF were suppressed by prior i.c.v. injection of indomethacin (100 micro g kg-1). In contrast, the i.v. injections of TNFR:Fc or indomethacin were ineffective. Our data suggest that LPS disturbs GI motility in sheep through a central pathway that involves TNF-alpha and prostaglandins sequentially.

To increase knowledge of the role of 5-hydroxytryptamine (5-HT) receptors in the regulation of reticuloruminal, omasal and antroduodenal myoelectric activity in sheep, the effects of 5-HT agonists on forestomach and antroduodenal myoelectric activity have been investigated in conscious sheep. 5-Carboxamidotryptamine, methysergide, alpha-methyl-5-HT, 2-methyl-5-HT, cisapride, zacopride or metoclopramide were infused intravenously for 5 min and myoelectric recordings were obtained from electrodes chronically implanted in the reticulum, rumen (dorsal sac), omasal body, abomasal antrum and duodenal bulb. The integrated activity of the reticular and ruminal spike bursts was modified only by the highest doses of alpha-methyl-5-HT, 2-methyl-5-HT, metoclopramide and cisapride. A phase III-like activity pattern was recorded in the antroduodenal area with all 5-HT-ergic agents and a dose-dependent inhibition of myoelectric activity was recorded in both reticulorumen and omasum at the same time as the antroduodenal effects. In the forestomach, methysergide alone induced inhibition of ruminal secondary contractions; 5-HT, alpha-methyl-5-HT, cisapride and metoclopramide, moreover, evoked an initial dose-dependent increase in antral activity. These results suggest that 5-HT1, 5-HT2, 5-HT3 and 5-HT4 receptors are involved in the regulation of the migrating myoelectric complex in sheep and in the genesis of forestomach hypomotility that is occasionally recorded concomitantly with the spontaneous duodenal phase III in sheep. 5-HT4 receptors also have a prokinetic action in the antral area.

We can suggest that ERK is involved in the mechanism of action of LPS in the intestine.