Bile acids inhibit Na⁺/H⁺ exchanger and Cl⁻/HCO3⁻ exchanger activities via cellular energy breakdown and Ca²âº overload in human colonic crypts.

Bile acids play important physiological role in the solubilisation and absorption of dietary lipids. However, under pathophysiological conditions, such as short bowel syndrome, they can reach the colon in high concentrations inducing diarrhoea. In this study, our aim was to characterise the cellular pathomechanism of bile-induced diarrhoea using human samples. Colonic crypts were isolated from biopsies of patients (controls with negative colonoscopic findings) and of cholecystectomised/ileum-resected patients with or without diarrhoea. In vitro measurement of the transporter activities revealed impaired Na⁺/H⁺ exchanger (NHE) and Cl⁻/HCO3⁻ exchanger (CBE) activities in cholecystectomised/ileum-resected patients suffering from diarrhoea, compared to control patients. Acute treatment of colonic crypts with 0.3 mM chenodeoxycholate caused dose-dependent intracellular acidosis; moreover, the activities of acid/base transporters (NHE and CBE) were strongly impaired. This concentration of chenodeoxycholate did not cause morphological changes in colonic epithelial cells, although significantly reduced the intracellular ATP level, decreased mitochondrial transmembrane potential and caused sustained intracellular Ca²âº elevation. We also showed that chenodeoxycholate induced Ca²âº release from the endoplasmic reticulum and extracellular Ca²âº influx contributing to the Ca²âº elevation. Importantly, our results suggest that the chenodeoxycholate-induced inhibition of NHE activities was ATP-dependent, whereas the inhibition of CBE activity was mediated by the sustained Ca²âº elevation. We suggest that bile acids inhibit the function of ion transporters via cellular energy breakdown and Ca²âº overload in human colonic epithelial cells, which can reduce fluid and electrolyte absorption in the colon and promote the development of diarrhea.

Cytotoxicity associated with induction of nitric oxide synthase in rat duodenal epithelial cells in vivo by lipopolysaccharide of Helicobacter pylori: inhibition by superoxide dismutase.

The products released by Helicobacter pylori (H. pylori) in the gastric antral and duodenal mucosa may be involved in mucosal ulceration by stimulating the local formation of cytotoxic factors such as nitric oxide (NO), superoxide or peroxynitrite. The present study investigates the ability of purified H. pylori lipopolysaccharide (LPS) to induce nitric oxide synthase (iNOS) in rat duodenal epithelial cells following in vivo challenge and its interaction with superoxide in promoting cellular damage and apoptosis. H. pylori LPS (0.75-3 mg kg(-1) i.v. or 3-12 mg kg(-1) p.o.) induced a dose - dependent expression of iNOS activity after 5 h in the duodenal epithelial cells, determined by [(14)C] arginine conversion to citrulline. The epithelial cell viability, as assessed by Trypan Blue exclusion and MTT conversion, was reduced 5 h after challenge with H. pylori LPS, while the incidence of apoptosis was increased. The iNOS activity and reduction in cell viability following H. pylori LPS challenge i.v. was inhibited by the selective iNOS inhibitor, 1400 W (0.2-5 mg kg(-1) i.v.). Concurrent administration of superoxide dismutase conjugated with polyethylene glycol (250 - 500 i.u. kg(-1), i.v.), which did not modify the cellular iNOS activity, reduced the epithelial cell damage provoked by i.v. H. pylori LPS, and abolished the increased incidence of apoptosis. These results suggest that expression of iNOS following challenge with H. pylori LPS provokes duodenal epithelial cell injury and apoptosis by a process involving superoxide, implicating peroxynitrite involvement. These events may contribute to the pathogenic mechanisms of H. pylori in promoting peptic ulcer disease.

Capsaicin-sensitive mechanisms in the modulation of rat colonic vascular permeability under physiological and pathological conditions.

Inflammatory bowel disease (IBD) causes a prolonged life-quality reduction of patients and high costs for health services. The aim of this study was to explore the possible involvement of peptidergic capsaicin-sensitive afferent nerves (CSN) in the pathogenesis of IBD. For the defunctionalization of colonic CSN, the lower part of the colon (1-4 cm from the anus) was exposed through a midline laparotomy and small pieces of gelfoam moistened with a solution of capsaicin (1%, 100 microL) was applied onto the serosal surface for 30 min in male Wistar rats. Colonic vascular permeability was assessed by measuring the extravasation of [125I] human serum albumin (2 microCi/kg, i.v., 2 h prior to killing). Two months after capsaicin treatment a significant increase in albumin extravasation was found in the lower (P < 0.005), but not in the upper (5-8 cm from the anus) part of the colon as compared to the sham-operated control. Intrarectal (8 cm from anus) administration of trinitrobenzene-sulphonic acid (TNBS; 30 mg/rat) induced similar plasma leakage in the lower and upper colon of control (CSN-intact) rats (P < 0.001) 1 week later. TNBS + ethanol (50%) produced further extravasation throughout the colon (P < 0.001) of CSN-intact animals. In the lower colon of capsaicin-pretreated rats TNBS-alone provoked an increase in plasma extravasation (P < 0.001) similar to that caused by TNBS + ethanol in CSN-intact rats. In the upper colon there was no difference in the effect of TNBS-alone on plasma leakage between control (CSN-intact) and CSN-depleted rats. The results suggest that capsaicin-sensitive nerves may play a significant protective/anti-inflammatory role in the colon under normal and pathological conditions.

Attenuation of Helicobacter pylori endotoxin-provoked rat intestinal inflammation by selective inhibition of the inducible nitric oxide synthase.

We studied the actions of purified Helicobacter pylori endotoxin (3 mg kg(-1), i.v.) on rat intestinal vascular permeability (assessed by the radiolabelled human serum albumin leakage technique) and on nitric oxide synthase induction (assessed by the citrulline assay) 4 h later. We found increased albumin leakage and expression of the inducible nitric oxide synthase in jejunum and colon, effects reversed by a selective inducible nitric oxide synthase inhibitor N-(8-(aminomethyl)benzyl)-acetamidine (1400W; 0.2-1 mg kg(-1), s.c., concurrently with endotoxin). Thus, H. pylori endotoxin seems to be capable of provoking an inflammatory response in the rat intestinal tissue. Systemic liberation of H. pylori endotoxin might possibly attenuate jejunal and colonic mucosal barrier function, a process mediated by the expression of the inducible nitric oxide synthase.

Vasopressin deficiency decreases the frequency of gastroduodenal ulceration in humans.

Vasopressin is a stress hormone released from the posterior pituitary. In humans suffering from central diabetes insipidus, this release of vasopressin is diminished. It was shown previously that the congenitally vasopressin-deficient Brattleboro homozygous rat is less sensitive to various ulcerogenic stimuli. In this study, we investigated the incidence of gastroduodenal ulceration in vasopressin deficient patients. Data on patients aged 20-70, hospitalized in Hungary between 1992 and 1995 were compared with those on the total population in this age group (6,681,020 in 1994). Subjects with central diabetes insipidus were selected separately (815 cases). Gastroduodenal ulceration was compared in subjects with an intact vasopressin release and vasopressin-deficient patients. The frequencies of gastroduodenal ulceration were also examined separately in male and female subjects. In the total population, the frequency of gastroduodenal ulceration was lower in vasopressin-deficient cases (2.22% versus 0.61%; P < 0.005). Among normal-vasopressin subjects, males have a higher risk of gastroduodenal ulceration than females (3.04% versus 1.46%, respectively; P < 0.001). Among vasopressin-deficient subjects, a similar male:female ratio was observed, but it was not significant (P = 0.36). In comparison to the normal-vasopressin population, the incidence of gastroduodenal ulceration was reduced among vasopressin-deficient males and females by 77% (P < 0.01) and by 82% (P < 0.05), respectively. In conclusion, endogenous vasopressin has a significant harmful action towards the human gastroduodenal mucosa. Peptide and non-peptide vasopressin receptor antagonists might have a potential therapeutic benefit in the treatment (as an adjuvant) and prevention of gastroduodenal ulceration.

Detrimental effects of oestradiol on cysteamine-induced gastroduodenal ulceration in the female rat.

The actions of the female sex steroid, oestradiol on cysteamine-induced mucosal ulceration has been evaluated in female Wistar rats. Administration of cysteamine (400 mg x kg(-1), s.c.) provoked macroscopic gastroduodenal mucosal injury (assessed planimetrically) and an increase in microvascular permeability (assessed by the extravasation of radiolabeled albumin) in the stomach and duodenum, determined 24 h later. Ovariectomy (2 weeks before cysteamine) reduced gastroduodenal macroscopic injury, and albumin extravasation following cysteamine challenge. Administration of oestradiol (1-5 mg x kg(-1), as an i.m. depot 1 week before cysteamine) dose-dependently augmented gastric and duodenal macroscopic mucosal lesions and microvascular permeability provoked by cysteamine. These findings indicate that oestradiol can exacerbate gastroduodenal ulceration and microvascular injury.

Endogenous vasopressin increases acute endotoxin shock-provoked gastrointestinal mucosal injury in the rat.

Administration of a low dose of endotoxin (from Escherichia coli, 3 mg kg(-1), i.v.), which does not affect vascular permeability or blood pressure over 1 h, leads to the release of endogenous vasopressin and damage to the mucosal microvasculature. Thus, endogenous vasopressin could be involved in septic shock. In the present study, we investigated the role of endogenous vasopressin in gastrointestinal mucosal injury induced by acute endotoxin shock, which was generated in rats by administering a high dose of E. coli endotoxin (50 mg kg(-1), i.v.). Tissues were removed 15 min after endotoxin. The vasopressin V1 receptor antagonist, d[CH2]5Tyr[Me]arginine-vasopressin (0.2-1 microg kg(-1), i.v.), was injected 10 min before endotoxin. Monastral blue (30 mg kg(-1), i.v.), which stains damaged vasculature, was injected 10 min before autopsy. Endotoxin reduced systemic arterial blood pressure (from 115+/-5 to 42+/-4 mmHg), generated macroscopic and microvascular injury, and elevated plasma vasopressin levels (from 3.4+/-0.2 to 178+/-16 pg ml(-1)). The vasopressin V1 receptor antagonist reduced this macroscopic injury, and in the vasopressin-deficient Brattleboro rat a similar reduction of gastrointestinal mucosal damage was found. Substantial decreases in endotoxin-induced microvascular damage were observed in each tissue, e.g., the gastric Monastral blue staining was reduced by 47+/-3% and 96+/-3% (P < 0.01) after vasopressin V1 receptor antagonist treatment and in Brattleboro rats, respectively. Vasopressin, acting through its V1 receptors, thus appears to be involved in acute endotoxin shock-provoked gastrointestinal injury.

Inducible nitric oxide synthase attenuates chronic colitis in human histocompatibility antigen HLA-B27/human beta2 microglobulin transgenic rats.

Rats transgenic for HLA-B27/human beta2-microglobulin develop a spontaneous multisystem inflammatory disorder that closely mimics human spondyloarthropathies. Prominent features of this disorder are gut inflammation that predominates in the colon, and arthritis. Several mediators such as IFN-gamma, IL-1beta, TNF-alpha, and inducible nitric oxide synthase (iNOS) have been found increased in the inflamed colonic mucosa. In the colon of HLA-B27 transgenic rats, iNOS is predominantly expressed by epithelial cells, and iNOS transcripts are detected in the hip cartilage of those rats, but not in nontransgenic littermates. The role of iNOS in this disorder was evaluated by administering the corticosteroid dexamethasone, or the NOS inhibitor L-N6-(1-iminoethyl)lysine (L-NIL) to HLA-B27 transgenic rats with established disease. Treatment with dexamethasone attenuated some aspects of gut inflammation, although it had no effect on iNOS expression. In contrast, treatment with L-NIL effectively inhibited iNOS activity, and resulted in an increase in colitis. Cytokine transcripts in the colon were modified by these treatments: IFN-gamma and IL-1beta were decreased after dexamethasone treatment, whereas administration of L-NIL resulted in decreased IFN-gamma, and TNF-alpha. A trend towards increased IL-1b expression was observed which could have contributed to the L-NIL pro-inflammatory effect. These results suggest that iNOS exerts a protective effect on colitis, in the inflammatory disorder of HLA-B27 transgenic rats.

Deleterious action of vasopressin in gastroduodenal ulceration: experimental and clinical observations.

Vasopressin, released from the posterior pituitary and from the vascular endothelium, can cause vasoconstriction and provoke platelet aggregation, leading to an impaired tissue blood supply. In humans with pituitary diabetes insipidus the central release of vasopressin is diminished, and in the Brattleboro homozygous rat there is congenitally no synthesis of this hormone. The gastroduodenal intramucosal vasopressin level is elevated in normal rats following various acute ulcerogenic challenges (after ethanol, reserpine, indomethacin, cold-restraint stress, endotoxin shock and hemorrhagic shock), and vasopressin-deficient rats are less sensitive to these stimuli. In a hospital- and population-based case-control, age-matched retrospective study, the incidence of human gastroduodenal ulceration is significantly higher in the normal population (in whom the release of vasopressin is presumed to be intact) than in the vasopressin-deficient one (central diabetes insipidus patients). In conclusion, endogenous vasopressin plays an aggressive role in development of gastroduodenal ulceration, especially that related to stress.

Predictors of relapse in patients with Crohn's disease in remission after 1 year of biological therapy.

BACKGROUND: Some of the most important questions relating to the use of biological therapy in inflammatory bowel diseases concern the duration of maintenance therapy. AIM: To assess the disease course and frequency of relapse of Crohn's disease (CD) following discontinuation of biological therapy, and to determine predictive factors for relapse. METHODS: One hundred twenty-one CD patients who had achieved clinical remission following 1 year of biological therapy and for whom biological therapy was then discontinued participated in this prospective observational study. Eighty-seven CD patients had received infliximab and 34 adalimumab. The definition of relapse was an increase of >100 points in CDAI to at least a CDAI of 150 points. RESULTS: Biological therapy was restarted within 1 year of treatment cessation in 45% of patients. Logistic regression analysis revealed that previous biological therapy (P = 0.011) and dose intensification during the 1-year course of biological therapy (P = 0.024) were associated with the need for and the time to the restarting of biological therapy. Smoking was observed to have an effect that was not statistically significant (P = 0.053). CONCLUSIONS: Biological therapy was restarted a median of 6 months after discontinuation in almost half of Crohn's disease patients in who had been in clinical remission following 1 year of biological therapy. These results suggest that, in the event of the presence of certain predictive factors, biological therapy should probably be continued for more than 1 year by most patients.

Is the efficacy of successful infliximab induction therapy maintained for one year lasting without retreatment in different behavior types of Crohn's disease?

UNLABELLED: The high cost of infliximab inhibits the regular retreatment of all patients in Hungary with Crohn's disease (CD) after beneficial induction therapy. This study is set out to evaluate the medium-term efficacy of induction therapy with infliximab without retreatment in CD patients with chronic activity and/or fistulae refractory to conventional therapy. METHODS: A retrospective 1-year review was undertaken of all CD patients with successfully induced remission or fistula closure with 3 infusions of infliximab. Infliximab was administered in a dose of 5 mg/kg 3 times, in weeks 0, 2 and 6. Clinical remission was defined as symptom resolution and an estimated Crohn's Disease Activity Index (CDAI) <150 and complete fistula closure. We evaluated the clinical response, the estimated CDAI, the number of draining fistulae, the dosages of steroid and immunosuppressive drugs at 6 and 12 months after the last infusion, and the needs for hospitalization and surgical intervention during this period. Breslow (Generalized Wilcoxon) test was used as the statistical method. RESULTS: The data of the 50 patients (19 luminal, 31 fistulizing disease; average age 29. 3 [13-59] years, disease localization: 23 colon, 13 ileum, 13 ileocolon, 1 duodenum) were suitable for analysis. Infliximab induction therapy without retreatment resulted in a beneficial effect lasting for at least 1 year in 22 of the 50 patients (44%). 11 of the 19 patients (57.9%) with luminal disease remained in steroid-free complete remission, while the fistulae persisted closed in only 11 of the 31 patients (35.5%) (p<0.05). CONCLUSION: Infliximab induction therapy alone may result in sustained remission mainly in patients with luminal disease. These results suggest the need for maintenance therapy with infliximab after successful therapy induction in patients with fistulae, while luminal CD patients could possibly participate in regular retreatment only if needed. If these data are confirmed, this modification of the therapeutic procedure could well increase the cost-effectiveness of infliximab.