Abstract: The lack of exposure to helminth infections, as a result of improved living standards and medical conditions, may have contributed to the increased incidence of IBD in the developed world. Epidemiological, experimental, and clinical data sustain the idea that helminths could provide protection against IBD. Studies investigating the underlying mechanisms by which helminths might induce such protection have revealed the importance of regulatory pathways, for example, regulatory T-cells. Further investigation on how helminths influence both innate and adaptive immune reactions will shed more light on the complex pathways used by helminths to regulate the hosts immune system. Although therapy with living helminths appears to be effective in several immunological diseases, the disadvantages of a treatment based on living parasites are explicit. Therefore, the identification and characterization of helminth-derived immunomodulatory molecules that contribute to the protective effect could lead to new therapeutic approaches in IBD and other immune diseases.
Abstract: BACKGROUND: It is well known that inflammation has a profound impact on the neuromuscular apparatus of the gastrointestinal tract during the inflammatory insult and in periods of remission, at the site of inflammation and at distance from this site. The importance of this interaction is illustrated by the higher prevalence of functional gut disorders in patients with inflammatory bowel disease. AIMS: To document the epidemiological and clinical significance of functional alterations of gut motility and sensitivity in patients with inflammatory bowel disease and to formulate potential pathophysiological mechanisms. RESULTS AND CONCLUSIONS: Functional gut disorders occur frequently in patients with inflammatory bowel disease, both during inflammatory episodes and in periods of remission, and have a major impact on their quality of life. The clinical manifestations of these motility and sensitivity disorders vary and are often difficult to treat, mainly because therapeutic guidelines and specific diagnostic tests to distinguish inflammatory bowel disease from functional gut disorders are lacking. Chronic bowel inflammation results in a complicated interaction between neuroendocrine serotonin-predominant cells of the mucosa, inflammatory cells (particularly mast cells) in the submucosa, the intrinsic and extrinsic innervation and the muscular apparatus including the interstitial cells of Cajal. The outcome of this interaction is a perturbation of gastrointestinal motor function, both locally and at distance from the site of inflammation and during both acute inflammation and remission.
Abstract: We present two cases of Down syndrome with inoperable esophageal cancer at a relatively young age. The first patient had a locally advanced squamous cell carcinoma of the distal esophagus. The second had a short circular adenocarcinoma of the distal esophagus with peritoneal and liver metastases. The cases are discussed with regard to the current literature on Down syndrome and esophageal cancer.
Abstract: Double-balloon enteroscopy is a novel technique for visualizing the entire small bowel. Complications have been reported relatively rarely in the small series published up until now. In this report we describe two patients who developed acute pancreatitis immediately after double-balloon enteroscopy, diagnosed on clinical, biochemical, and radiological grounds. In both patients the pancreatitis resolved with supportive care. Based on early studies on the pathogenesis of acute pancreatitis, we discuss the possible pathogenetic mechanism for pancreatitis arising as a complication of this novel endoscopic technique.
Abstract: The incidence of atopic and immune diseases has dramatically increased during the second half of the twentieth century. This has been attributed to improved sanitation and hygiene with reduced exposure to infections. The concept of this hygiene hypothesis is not new, and is currently used to explain the increasing incidence of a wide area of diseases. Parasitic helminths are powerful modulators of their host's immune system. It is suggested that the reduced exposure to helminths, due to better hygiene conditions, may predispose to the development of inflammatory bowel diseases. This article reviews the current epidemiological, experimental and clinical data supporting the role of helminths in the hygiene hypothesis in inflammatory bowel diseases.
Abstract: Crohn's disease and ulcerative colitis are chronic relapsing inflammatory bowel diseases (IBDs). Different pharmacological agents are currently used in several combinations to control the inflammatory process. Recently, antibodies against the proinflammatory cytokine tumor necrosis factor-alpha appeared to be very effective in treating patients with Crohn's disease. However, due to the fact that the pathogen causing IBD is still unknown, no causative treatment is currently available that is able to make the disease disappear. Recently, the hygiene hypothesis of the development of immunological diseases was proposed, stating that raising children in extremely hygienic environments with less exposure to parasite infections may negatively affect the development of the immune system, predisposing them to immunologic diseases such as IBD. This hypothesis is supported by experimental data showing that helminthic parasites protect against T helper (TH) type 1 cell-mediated gastrointestinal inflammations like Crohn's disease. Both TH-2 cells and regulatory T cells may be involved in this immunomodulatory mechanism. Here, we review the experimental and clinical studies in favor of the hygiene hypothesis, opening perspectives on new therapies for IBD.
Abstract: BACKGROUND AND AIMS: Crohn's disease, characterised by chronic T helper 1 (Th1) inflammation and dysmotility of the gut, is most prevalent in developed countries. Parasitic infections are most prevalent in developing countries and induce a T helper 2 (Th2) immune response. We hypothesised that this Th2 immune response protects against Th1 gut inflammation. METHODS: The parasite Schistosoma mansoni induces a transient Th2 immune response in the semipermissive rat host. 2,4,6-Trinitrobenzene sulphonic acid (TNBS) induced colitis is an experimental model of Th1-like gut inflammation. The effect of concurrent infection with S mansoni on the course of TNBS induced colitis was assessed using macroscopic and microscopic damage scores, histology, myeloperoxidase (MPO) activity assay, cytokine production assay, and by studying in vitro contractility of longitudinal and circular colonic muscle strips. RESULTS: TNBS induced colitis that spontaneously healed after four weeks. Concurrent infection with S mansoni significantly reduced the duration of TNBS induced colitis to two weeks, as shown by macroscopic and microscopic damage scores and by a faster decrease in colonic MPO activity. TNBS increased colonic interleukin 2 (IL-2) production whereas S mansoni increased splenic IL-4 and IL-2 levels. Contractility of longitudinal and circular muscle strips was maximally inhibited one week after TNBS and normalised after three weeks. After four weeks, longitudinal muscle strip contractility was significantly increased. Concurrent infection with S mansoni normalised longitudinal muscle contractility after one week whereas circular muscle contractility remained inhibited. CONCLUSIONS: Concurrent infection with S mansoni significantly attenuates TNBS induced colitis in the rat. Inflammation induced disturbances in contractility of longitudinal and circular colonic muscle strips may outlast the inflammatory reaction.
Abstract: The treatment of choice for epiretinal membranes (ERM) causing marked retinal distortion and substantial visual impairment remains vitreoretinal surgery. The purpose of this study was to evaluate the results of surgery performed in our department and to investigate the prognostic value of different factors such as preoperative best-corrected visual acuity (BCVA), pre-existing cystoid macular edema (CME), intra-operative peeling of the internal limiting membrane (ILM), age and duration of symptoms. Eighty-eight consecutive eyes of 88 patients were operated on for ERM from July 1998 to June 2000. Both idiopathic and secondary cases were included. In all cases the ERM was successfully removed from the fovea. Mean BCVA after surgery increased from Snellen 0.2 (hand motion (HM) - 0.6) to Snellen 0.5 (HM - 1.0) (p<0.0001). Our results confirm the efficacy of surgical removal of the ERM in improving the visual acuity. Although not statistically significant, mean postoperative BCVA was slightly better in the group without pre-existing CME (p>0.05) and in the group where peeling of the ILM was performed (p>0.05). The data suggest that early surgery is likely to decrease the risk of developing irreversible macular damage (p<0.05). Because accelerated nuclear sclerosis with visual impairment is a common phenomenon after vitrectomy, one might consider performing a phaco-emulsification at the same time, especially in the elderly.
Abstract: Nitric oxide (NO) is postulated to play a role in endotoxin-induced ileus. We investigated the effect of selective blockade of inducible NO synthase (iNOS) and guanylyl cyclase on endotoxin-induced ileus in mice. Thirty minutes before injection of lipopolysaccharides (LPS), mice were pretreated with L-NAME (N omega-nitro-L-arginine methyl ester, non-selective NOS inhibitor), 1400W (N-(3-(aminomethyl)benzyl)acetamide, selective iNOS inhibitor), ODQ (1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one, guanylyl cyclase inhibitor), dimethyl sulfoxide (DMSO, vehicle), or dexamethasone. After 18 h, general well being deteriorated and the mice developed hypothermia and a significant delay in gastric emptying and intestinal transit as measured by Evans blue. 1400W completely reversed the endotoxin-induced delay in gastric emptying, while L-NAME did not have these beneficial effects. On the contrary, even in control mice, L-NAME delayed gastric emptying. Dexamethasone, DMSO, and ODQ mimicked the effect of 1400W on endotoxin-induced delay in gastric emptying. The endotoxin-induced delay in transit was significantly improved only by 1400W. None of the drugs reversed the hypothermia. In LPS mice treated with L-NAME, the behavior scale increased even further, while it decreased after treatment with 1400W. In conclusion, selective inhibition of iNOS reverses the endotoxin-induced delay in gastric emptying and transit and improves general well being. The pathway used by NO, derived from iNOS, may involve inhibition of guanylyl cyclase or radical scavenging.
Abstract: In Schistosoma mansoni-infected mice, gastrointestinal transit was measured in vivo and the neuromuscular function of longitudinal muscle strips of inflamed ileum and noninflamed gastric fundus was assessed in vitro. Eight weeks after infection, the ileal wall was acutely inflamed, as shown by a mucosal inflammatory infiltrate, leading to an increase in mucosal thickness, in myeloperoxidase (MPO) activity, and in interleukin (IL)-1beta production. At that time, both gastrointestinal transit and in vitro ileal contractility were normal. Twelve weeks after infection, chronic granulomatous inflammation led to proliferation of the muscle layer and to a further increase in MPO activity, whereas IL-1beta production normalized. Gastrointestinal transit was decreased, whereas in vitro ileal contractility was increased irrespective of the contractile stimulus. In vitro incubation with IL-1beta (10 ng/ml for 60 min) significantly increased ileal contractility only at 8 wk after infection. Indomethacin, tetrodotoxin, and atropine had no differential effect on ileal contractility in controls and infected mice. In vitro contractility of noninflamed gastric fundus was normal both 8 and 12 wk after infection. We conclude that intestinal schistosomiasis 8 wk after infection is associated only with structural changes of the ileum, whereas 12 wk after infection, both structural and functional changes are present. These changes are characterized by increased ileal wall thickness, decreased gastrointestinal transit, and increased smooth muscle contractility restricted to the inflamed gut segment.
Abstract: 1. Electrical field stimulation (EFS) of non-adrenergic non-cholinergic nerves of the mouse gastric fundus induced frequency-dependent transient relaxations which were mimicked by nitric oxide (NO), added as acidified NaNO(2). The NO donors S-nitrosocysteine, S-nitrosoglutathione, SIN-1 and hydroxylamine induced sustained concentration-dependent relaxations. The NO synthase blocker L-nitro arginine (L-NOARG; 300 microM) abolished the relaxations to EFS without affecting the relaxations to NO. 2. The copper(I) chelator neocuproine (10 microM) enhanced the relaxations to EFS and NO but inhibited those to S-nitrosocysteine and S-nitrosoglutathione. Neocuproine potentiated the relaxations to SIN-1, which releases NO extracellularly, without affecting the relaxations to hydroxylamine, which releases NO intracellularly. 3. The potentiating effect of neocuproine on the relaxations to EFS was more pronounced after inhibition of catalase with 3-amino-1,2,4-triazole (1 mM) but not after inhibition of Cu/Zn superoxide dismutase (SOD) with diethyl dithiocarbamic acid (DETCA, 1 mM). The potentiating effect of neocuproine on relaxations to NO was not altered by 3-amino-1,2,4-triazole or DETCA treatment. 4. The relaxations to EFS were significantly inhibited by the oxidants hydrogen peroxide (70 microM) and duroquinone (10 microM) but only after inhibition of catalase with 3-amino-1,2,4-triazole or after inhibition of Cu/ZnSOD with DETCA respectively. 5. Our results suggest that neocuproine can act as an antioxidant in the mouse gastric fundus and that both catalase and Cu/ZnSOD protect the nitrergic neurotransmitter from oxidative breakdown. Since inhibition of catalase but not inhibition of Cu/ZnSOD potentiated the effect of neocuproine on relaxations to EFS without affecting the relaxations to NO, catalase may protect the nitrergic neurotransmitter mainly at a prejunctional site whereas Cu/ZnSOD protects at a postjunctional site.
Abstract: The effect of chronic granulomatous inflammation of the intestine was studied on the prejunctional modulation of cholinergic nerve activity in the mouse ileum. Contractions to carbachol (0.01 - 0.3 microM) and to electrical field stimulation (EFS, 0.25 - 8 Hz) of enteric neurons were higher in inflamed ileum as compared to control ileum. However, when the neurally-mediated contractions to EFS were expressed as percentage of the direct smooth muscle contraction to carbachol, the responses to EFS were similar in control and inflamed ileum. Atropine (1 microM) abolished all contractions to EFS and carbachol in control and inflamed ileum. DMPP (3 - 30 microM), a nicotinic receptor agonist, induced concentration-dependent contractions that were more pronounced in inflamed ileum as compared to control ileum. Hexamethonium (100 microM), a nicotinic receptor blocker, significantly inhibited the contractions to EFS in inflamed ileum but not in control ileum. In control ileum, histamine (10 - 100 microM) and the histamine H(1) receptor agonist HTMT (3 - 10 microM) inhibited the contractions to EFS concentration-dependently without affecting the contractions to carbachol. The inhibitory effect of histamine and HTMT was prevented by the histamine H(1) antagonist mepyramine (5 - 10 microM) but not by the H(2)- and H(3)-receptor antagonists cimetidine and thioperamide (both 10 microM). In chronically inflamed ileum however, histamine (10 - 100 microM) and HTMT (3 - 10 microM) failed to inhibit the contractions to EFS. The histamine H(2) and H(3) receptor agonists dimaprit and R(-)-alpha-methylhistamine did not affect the contractions to EFS in control and inflamed ileum. The alpha(2)-receptor agonist UK 14.304 (0.01 - 0.1 microM) inhibited the contractions to EFS in control and inflamed ileum without affecting the contractions to carbachol. The effect of UK 14.304 was reversed by the alpha(2)-receptor antagonist yohimbine (1 microM). The inhibitory effect of UK 14.304 on contractions to EFS was of similar potency in control and inflamed ileum. Our results suggest that the prejunctional modulation of cholinergic nerve activity by nicotinic and histaminic H(1) receptors is disturbed during chronic intestinal inflammation whereas the modulation by alpha(2)-receptors is preserved. Such a disturbance of cholinergic nerve activity may contribute to the motility disturbances that are often observed during chronic intestinal diseases in humans.
Abstract: Intraluminal instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS) in ethanol is a classical model of colitis in the rat. Little is known about the time-related effect of TNBS on the contractility and morphology of the rat ileum. After 36 h, TNBS induced acute ileitis. Spontaneous activity of longitudinal muscle strips was decreased, as were receptor- and nonreceptor-mediated contractions and contractions induced by electrical stimulation. After 1 week, mucosal integrity was restored, although the thickness of both mucosal and muscle layers was increased. Spontaneous activity, receptor- and nonreceptor-mediated contractions and electrically induced contractions of longitudinal muscle strips were increased due to hypertrophy and hyperplasia of smooth muscle cells. This was confirmed in the contractility study of individual muscle cells. Functional alterations after 1 week were restricted to a decreased response to substance P. TNBS-ileitis in the rat lacks a chronic phase and is accompanied by functional hypocontractility of longitudinal smooth muscle cells during the acute inflammation, whereas the contractility of the longitudinal muscle layer is increased in the postinflammation phase due to structural alterations. There is a selective inhibition of the response to substance P in the postinflammation phase.
Abstract: Inflammation leads to intestinal dysmotility which can be due to both functional and trophic alterations of the neuromuscular apparatus. To discriminate between trophic and functional changes, several normalization procedures are used in contractility studies. It is important to know how normalization procedures may influence the obtained results. In a rat model of TNBS-induced ileitis, we compared seven known normalization procedures for pharmacological contractions of longitudinal muscle strips. During acute ileitis, contractility was significantly decreased, irrespective of the normalization procedure used. During the post-inflammation phase, hypertrophy and hyperplasia of smooth muscle cells led to increased contractility on raw strip chart recordings. However, when contractions were corrected for the increase in muscle mass, the contractility was either normal or decreased, depending on the normalization procedure used. Normalization of contractions to the cross-sectional area (CSA) of the longitudinal muscle is the gold standard. Comparison of three methods to determine the CSA, showed that the commonly used equation to calculate the CSA, based on the tissue weight, length and density, might overestimate the CSA. We conclude that this equation should be adapted by a muscle thickness ratio, or alternatively the CSA can be determined on histological sections.
Abstract: During intestinal inflammation, motility disturbances are not restricted to inflamed regions, but may also occur in remote non-inflamed sites of the gastrointestinal tract. Our aim was to investigate the motor function of the gastric fundus after the induction of terminal ileitis in the rat. Ileal inflammation was induced by intraluminal installation of 2,4,6-trinitrobenzenesulphonic acid (TNBS) into the ileum. Inflammation was assessed both histologically and biochemically. Contractions and relaxations of longitudinal muscle strips from the gastric fundus were studied 36 h and 1 week later. During the acute phase of ileal inflammation (36 h), the non-inflamed stomach was distended. The contractility of longitudinal muscle strips of the gastric fundus was decreased due to a post-receptor defect. In addition, nonadrenergic noncholinergic (NANC) relaxations were inhibited due to neuronal dysfunction. Aortic contractility remained normal and the mere presence of food in the stomach did not account for the disturbed neuromuscular function in the gastric fundus. Ablation of extrinsic primary afferent neurones by capsaicin further impaired gastric fundus contractility. Transection and re-anastomosis of the jejunum reversed the effect of TNBS-induced ileitis on the neuromuscular function of the gastric fundus. One week after TNBS, cholinergic neurotransmission was increased in the gastric fundus. During acute ileitis, smooth muscle cell contractility and inhibitory NANC neurotransmission are inhibited in the non-inflamed gastric fundus. This phenomenon may be mediated by intrinsic connections within the enteric nervous system.
Abstract: Schistosomiasis mansoni is a major health problem, mainly occurring in developing countries. A large proportion of infected individuals suffers from motility-related gastrointestinal problems. In the present study, the diffuse inflammatory response in the small bowel wall, as compared to the egg-induced granulomatous inflammation, was investigated. For this purpose, OF1 mice infected with Schistosoma mansoni 8-16 weeks prior to the experiment, and uninfected control mice were studied. The ileum showed both a diffuse mucosal inflammation as well as a granulomatous reaction. The diffuse mucosal inflammation caused an increase in the thickness of the mucosa, with blunting of the villi. A significant, transient increase of thickness of the muscularis propria after 12 weeks of infection was noted. There was an infection-related mast cell infiltrate in the muscularis propria, consisting of formalin fixation-insensitive connective tissue mast cells. Ganglionitis of the myenteric plexus was noted. Rarely, ganglia of the myenteric plexus contained apoptotic cells. A general pharmacological set of experiments showed a significant increase in intestinal contractility, both to exogenously administered, as well as to endogenously released neurotransmitters. Our results demonstrate that S. mansoni infection in the mouse ileum leads to diffuse specific enteric inflammation that is associated with an enhanced response to contractile agents.
Abstract: In the present study, we investigated the cellular components that are involved in the release of nitric oxide (NO) from S-nitrosothiols and whether these components also modulate the activity of the nitrergic neurotransmitter in the rat gastric fundus. Electrical stimulation of nitrergic nerves induced frequency-dependent transient relaxations which were mimicked by exogenous NO. The S-nitrosothiols S-nitrosocysteine, S-nitrosoglutathione and S-nitroso-N-acetylpenicillamine induced concentration-dependent relaxations which were generally more sustained as compared to those to nitrergic nerve stimulation or NO. The relaxations to nitrergic nerve stimulation and those to NO were significantly enhanced by the copper(I) chelator neocuproine but not affected by the copper(II) chelator cuprizone. The relaxations to the S-nitrosothiols were significantly inhibited by neocuproine but not by cuprizone. The antioxidant ascorbate did not affect the tension of the muscle strip. However, in the presence of an S-nitrosothiol, ascorbate induced an immediate, sharp and transient relaxation that was significantly inhibited by a low concentration of neocuproine but not by cuprizone. Ascorbate did not induce a relaxation during short-train or prolonged nerve stimulation of the muscle strip. These results suggest that ascorbate interacts with copper to modulate the biological activity of S-nitrosothiols but not that of the nitrergic neurotransmitter. The differential effect of neocuproine indicates that S-nitrosothiols do not mediate the nitrergic neurotransmission of the rat gastric fundus. As neocuproine is to date the only compound that exerts an opposite effect on the biological activity of the nitrergic neurotransmitter and on that of S-nitrosothiols, it may be useful to elucidate the nature of the nitrergic neurotransmitter in the peripheral nervous system.
Abstract: BACKGROUND/AIM: The effects of different prokinetic agents, the motilide erythromycin and the substituted benzamides metoclopramide and cisapride, were investigated in a rat model of postoperative ileus. These effects were compared with that of granisetron, a 5-hydroxytryptamine (5-HT(3)) receptor antagonist, and a novel enterokinetic agent, prucalopride, a 5-HT(4) receptor agonist. METHODS: Different degrees of inhibition of gastrointestinal transit, measured by the migration of Evans blue, were achieved by skin incision, laparotomy, or laparotomy plus mechanical stimulation of the gut. RESULTS: Metoclopramide decreased the transit after laparotomy with or without mechanical stimulation, whereas cisapride increased it after all three operations. Granisetron had no effect on the transit after the three operations when given alone. Prucalopride tended to increase the transit after laparotomy with or without mechanical stimulation when given alone. However, statistical significance was only reached when prucalopride was combined with granisetron. Erythromycin, a motilin receptor agonist, did not improve postoperative ileus in the rat. CONCLUSIONS: Cisapride, but not metoclopramide or erythromycin, is able to improve postoperative ileus in the rat. The results suggest that a combination of 5-HT(3) receptor antagonist and 5-HT(4) receptor agonist properties may be required to obtain a beneficial effect on surgery induced ileus in the rat. Furthermore, they indirectly indicate that stimulation of the excitatory mechanisms is not able to overcome the inhibitory influence of the neural reflex pathways activated during abdominal surgery.
Abstract: 1. The effects of the antioxidants ascorbic acid and alpha-tocopherol and of the metal chelator ethylenediaminetetraacetic acid (EDTA) were studied on relaxations in response to S-nitrosothiols, authentic nitric oxide (NO) and nitrergic non-adrenergic non-cholinergic stimulation of the rat gastric fundus. 2. The S-nitrosothiols S-nitrosocysteine (1-100 nM), S-nitrosoglutathione (0.01-3 microM) and S-nitroso-N-acetylpenicillamine (0.01-3 microM) induced concentration-dependent relaxations of the rat gastric fundus muscle strips, which were precontracted with prostaglandin F2alpha. The relaxations to all S-nitrosothiols were concentration-dependently enhanced by the antioxidants ascorbic acid (0.1-3 microM) and alpha-tocopherol (3-30 microM) and inhibited by the metal chelator EDTA (26 microM). 3. Ascorbic acid and alpha-tocopherol alone did not induce a relaxation of the precontracted rat gastric fundus muscle strip. However, when ascorbic acid (1 microM) or alpha-tocopherol (1 microM) were injected in the organ bath 1 minute after S-nitrosoglutathione (0.1 microM) or after S-nitroso-N-acetylpenicillamine (0.1 microM), they induced an immediate, sharp and transient relaxation. This relaxation was inhibited by the superoxide generator pyrogallol (2 microM). Such a relaxation to ascorbic acid or alpha-tocopherol was not observed in the presence of S-nitrosocysteine (10 nM). 4. Electrical field stimulation (0.5-4 Hz) of the precontracted rat gastric fundus strips induced frequency-dependent nitrergic relaxations which were mimicked by authentic NO (3-300 nM) and by acidified sodium nitrite NaNO2 (0.3-10 microM). Ascorbic acid (0.33-3 microM), alpha-tocopherol (3-30 microM) or EDTA (26 microM) did not affect the relaxations to nitrergic stimulation, NO or NaNO2. 5. In summary, relaxations to S-nitrosothiols in the rat gastric fundus are enhanced by the antioxidants ascorbic acid and alpha-tocopherol and inhibited by the metal chelator EDTA. However, relaxations to nitrergic stimulation of the rat gastric fundus or those to authentic NO were not affected by the antioxidants or by the metal chelator. These results indicate that antioxidants and metal chelators have a different effect on the biological activity of S-nitrosothiols and on that of the nitrergic neurotransmitter. Therefore, our results suggest that S-nitrosothiols do not act as intermediate compounds in nitrergic neurotransmission in the rat gastric fundus.
Abstract: The effect of two prostaglandin biosynthesis inhibitors and their interaction with the L-arginine/nitric oxide (NO) pathway was investigated in a rat model of experimental ileus. The gastrointestinal transit was measured as the migration of Evans blue after three different operations. Indomethacin completely reversed the additional inhibition of the transit induced by mechanical stimulation of the gut. Ketorolac completely reversed the inhibition of the transit induced by the laparotomy, but had no additional effect on the inhibition induced by mechanical stimulation of the gut. Administration of indomethacin plus L-nitroarginine or L-arginine could not enhance or prevent the effect of indomethacin alone. Administration of ketorolac and L-nitroarginine completely reversed the transit after the laparotomy plus manipulation whereas ketorolac plus L-arginine had no additional effect as compared to ketorolac alone. From these findings we conclude that in addition to NO, prostaglandins are involved in the pathogenesis of postoperative ileus in the rat. However, indomethacin and ketorolac differentially affect postoperative ileus suggesting that prostaglandins are involved in different pathogenic mechanisms leading to postoperative ileus.
Abstract: 1. Vasoactive intestinal polypeptide (VIP) is an inhibitory neurotransmitter in the enteric nervous system. We investigated the role of VIP1/PACAP receptors in postoperative ileus in rats. 2. Different degrees of inhibition of the gastrointestinal transit, measured by the migration of Evans blue, were achieved by skin incision, laparotomy or laparotomy plus mechanical stimulation of the gut. 3. The transit after skin incision or laparotomy was not altered by the VIP1/PACAP receptor antagonist Ac-His1,D-Phe2, K15, R16, VIP(3-7), GRF(8-27)-NH2 nor by the VIP1/PACAP receptor agonist K15, R16, VIP(1-7), GRF(8-27)-NH2 and the VIP2/PACAP receptor agonist RO 25-1553 (5 microg kg(-1)). 4. However, the transit after laparotomy plus mechanical stimulation was significantly enhanced by the VIP1/PACAP receptor antagonist, whereas it was further inhibited by the VIP1/PACAP receptor agonist. The combination of the VIP1/PACAP receptor agonist and antagonist counteracted the effect of both drugs alone. The VIP2/PACAP receptor agonist did not alter the effect of the VIP1/PACAP receptor antagonist. 5. The combination of the VIP1/PACAP receptor antagonist plus the nitric oxide (NO) synthase inhibitor L-nitroarginine had no effect on the transit after laparotomy plus mechanical stimulation, while the transit after skin incision was significantly decreased. 6. These findings suggest the involvement of VIP1/PACAP receptors, next to NO, in the pathogenesis of postoperative ileus. However, the combination of the VIP1/PACAP antagonist and the NO synthase inhibitor abolished the beneficial effect of each drug alone, suggesting the need for one of the inhibitory neurotransmitters to enable normal gastrointestinal transit.
Abstract: 1. In a rat model of experimental ileus, the effect of blockade of adrenergic and nitrergic neurotransmission was studied on the intestinal transit of Evans blue. 2. Ether anaesthesia and skin incision had no influence on the transit. Laparotomy significantly inhibited the transit of Evans blue. This inhibition was even more pronounced when the small intestine was manipulated. 3. Reserpine (5 mg kg-1), a drug that blocks adrenergic neurotransmission, completely reversed the inhibition of the transit induced by laparotomy but only partially reversed that induced by laparotomy with manipulation of the small intestine. 4. N omega-nitro-L-arginine (L-NOARG, 5 mg kg-1), a nitric oxide synthase inhibitor, completely reversed the reserpine-resistant inhibition induced by laparotomy with manipulation of the small intestine. The effect of L-NOARG was prevented by concomitant administration of L-arginine. L-Arginine itself slightly, but significantly enhanced the inhibition. S-methylisothiourea and aminoguanidine, selective inhibitors of the inducible NO synthase, had no effect on the transit after the three operations. 5. Treatment of the rats with reserpine plus L-NOARG had no additional effect on the transit after laparotomy as compared to reserpine alone. However, reserpine plus L-NNA completely reversed the inhibition of the transit induced by laparotomy with manipulation of the small intestine. 6. These findings support the involvement of adrenergic pathways in the pathogenesis of ileus and suggest that the additional inhibitory effect of mechanical stimulation results from an enhanced release of NO by the constitutive NO synthase.
Abstract: In a rat model of postoperative ileus, induced by abdominal surgery, we investigated the effect of mu- and kappa-opioid receptors. Different degrees of inhibition of the gastrointestinal transit, measured by the migration of Evans blue, were achieved by skin incision, laparotomy or laparotomy plus manipulation of the gut. Morphine (1 mg/kg), a preferential mu-opioid receptor agonist, significantly inhibited the transit after skin incision, while the transit after the laparotomy with or without manipulation was not significantly affected. Fedotozine (5 mg/kg), a peripheral kappa-opioid receptor agonist, enhanced the transit after laparotomy plus manipulation, while naloxone (1 mg/kg), a non-specific opioid receptor antagonist, further inhibited the transit after laparotomy plus manipulation. Naloxone and fedotozine alone had no effect on the transit after skin incision or laparotomy without manipulation. However, naloxone prevented the effect of morphine on the transit after skin incision and of fedotozine on the laparotomy plus manipulation. These results support a role for peripheral kappa-opioid receptors in the pathogenesis of postoperative ileus induced by abdominal surgery.
Abstract: Based on organ bath experiments illustrating nitric oxide (NO) or an NO-releasing substance as mediator of the nonadrenergic noncholinergic (NANC) nerve-induced relaxations in the canine ileocolonic junction and rat gastric fundus, a bioassay superfusion technique was developed to detect and characterize the inhibitory NANC neurotransmitter. Evidence is provided that NANC nerve stimulation results in the release of a vasorelaxant factor with pharmacological properties similar to NO: its release is blocked by inhibition of the NO biosynthesis and tetrodotoxin, but enhanced by L-arginine. Its half-life is comparable to that of NO, and its biological activity is enhanced by superoxide dismutase, but abolished by hemoglobin. In addition, the nitrergic transferable factor is similarly affected as authentic NO by pyrogallol, hydroquione, hydroxocobalamin and L-cysteine. Nitrosothiols, like S-nitroso-L-cysteine, S-nitrosoglutathione and S-nitroso-N-acetyl-D,L- penicillamine, on the other hand, have a different pharmacological profile compared to NO and the nitrergic factor, indicating that NO, and not a nitrosothiol, is released from inhibitory NANC nerves in the canine ileocolonic junction. This nerve-induced release is Ca(2+)-dependent and prejunctionally regulated by K+ channels and alpha 2-adrenoceptors: blockade of K+ channels enhances the release, whereas alpha 2-adrenoceptor activation reduces the release of the nitrergic factor, possibly by activating K+ channels.
Abstract: The effects of pretreatment with the nitric oxide (NO)-releasing substances 3-morpholino-sydnoninime (SIN-1) and nitroglycerin were investigated on relaxations induced by non-adrenergic non-cholinergic (NANC) nerve stimulation, authentic NO and vasoactive intestinal polypeptide (VIP) in the rat gastric fundus. Short periods of electrical stimulation (0.5-16 Hz, 1 ms, pulse trains of 10 s) induced frequency-dependent transient relaxations, previously shown to be mainly mediated by NO. Both SIN-1 (10-100 microM) and nitroglycerin (0.5 mM) pretreatment significantly reduced these electrically induced responses to a similar extent as the inhibitor of the NO biosynthesis L-nitroarginine (30-300 microM). Prolonged periods of electrical stimulation (16 Hz, 1 ms, pulse trains of 180 s) induced a sustained relaxation, previously shown to be mediated by NO and VIP. L-Nitroarginine (30-300 microM) or pretreatment with SIN-1 (100 microM) or nitroglycerin (0.5 mM) did not affect the amplitude of this relaxation but slowed down its onset. Authentic NO (0.01-10 microM) and VIP (0.01-10 nM) induced respectively transient and sustained concentration-dependent relaxations. SIN-1 or nitroglycerin pretreatment had no effect on the concentration-response curves to NO and VIP. These results indicate that prolonged exposure to NO donors inhibits electrically induced nerve-mediated NANC relaxations without affecting the postjunctional response to NO and VIP. As similar results are obtained with NO biosynthesis inhibitors, our results illustrate a prejunctional inhibitory effect of NO on the NANC nerves of the rat gastric fundus and suggest the presence of an autoregulatory mechanism for the nitrergic innervation.
Abstract: 1. In organ bath experiments, hydroquinone (30-100 microM) and hydroxocobalamin (30-100 microM) concentration-dependently inhibited the relaxations induced by NO (0.3-30 microM) but not those by nitroglycerin (GTN, 1 microM) in the canine ileocolonic junction (ICJ). Hydroxocobalamin reduced the relaxation to low frequency (2 Hz) stimulation of the non-adrenergic, non-cholinergic (NANC) nerves, whereas hydroquinone only reduced the NANC nerve-mediated relaxations to electrical stimulation at 16 Hz, 0.5 ms. 2. Relaxations to S-nitroso-L-cysteine (CysNO, 1-30 microM), or S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 1-30 microM) were not inhibited by hydroquinone (30-100 microM), hydroxocobalamin (30-100 microM), pyrogallol (30-100 microM) or L-cysteine (1-3 microM). Hydroquinone (100 microM) only reduced the relaxation to 10 microM CysNO. Hydroxocobalamin, but not hydroquinone, pyrogallol or L-cysteine, potentiated the relaxations to the lowest concentration (1 microM) of S-nitrosoglutathione (GSNO, 1-30 microM). 3. In the superfusion bioassay, hydroquinone (100 microM) and hydroxocobalamin (1 microM) concentration-dependently inhibited the biological activity of authentic NO (1-4 pmol) to the same extent as that of the transferable nitrergic factor, released from the canine ICJ in response to NANC nerve stimulation (8-16 Hz, 2 ms). Responses to GTN (10 pmol) or adenosine 5'-triphosphate (10 nmol) were not affected. 4. In conclusion, the nitrosothiols CysNO, SNAP and GSNO relax the canine ileocolonic junction, but these relaxations, pharmacologically, behave differently from the NANC nerve-mediated relaxations.(ABSTRACT TRUNCATED AT 250 WORDS)
