Involvement of iNOS-induced reactive enteric glia cells in gastrointestinal motility disorders of postoperative Ileus mice

Postoperative ileus (POI) is the cessation or reduction of gastrointestinal (GI) motility after surgery. Reactive enteric glial cells (EGCs) are critical for maintaining bowel function. However, the triggering mechanisms and downstream effects of reactive EGCs in POI were poorly understood. The goal of this current study was to investigate whether the inducible nitric oxide synthase (iNOS)-driven reactive EGCs participated in GI motility disorders and mechanisms underlying altered GI motility in POI. Intestinal manipulation (IM)-induced POI mice and iNOS-/- mice were used in the study. Longitudinal muscle and myenteric plexuses (LMMPs) from the distal small intestine were stained by immunofluorescence. Our results found that the GI motility disorders occurred in the IM-induced POI mice, and reactive EGCs were observed in LMMPs. Glial metabolic inhibitor gliotoxin fluorocitrate (FC) treatment or iNOS gene knockout attenuated GI motility dysfunction. In addition, we also found that FC treatment or iNOS gene knockout significantly inhibited the fluorescence intensity macrophage colony-stimulating factor (M-CSF), which reduced M2 phenotype macrophages activation in LMMPs of IM-induced POI mice. Our findings demonstrated that iNOS-driven reactive EGCs played a key role and were tightly linked to the MMs homeostasis in the POI mice. EGCs are emerging as a new frontier in neurogastroenterology and a potential therapeutic target.

BQ788 reveals glial ETB receptor modulation of neuronal cholinergic and nitrergic pathways to inhibit intestinal motility: Linked to postoperative ileus

BACKGROUND AND PURPOSE

ET-1 signalling modulates intestinal motility and inflammation, but the role of ET-1/ETB receptor signalling is poorly understood. Enteric glia modulate normal motility and inflammation. We investigated whether glial ETB signalling regulates neural-motor pathways of intestinal motility and inflammation.

EXPERIMENTAL APPROACH

We studied ETB signalling using: ETB drugs (ET-1, SaTX, BQ788), activity-dependent stimulation of neurons (high K+ -depolarization, EFS), gliotoxins, Tg (Ednrb-EGFP)EP59Gsat/Mmucd mice, cell-specific mRNA in Sox10CreERT2 ;Rpl22-HAflx or ChATCre ;Rpl22-HAflx mice, Sox10CreERT2 ::GCaMP5g-tdT, Wnt1Cre2 ::GCaMP5g-tdT mice, muscle tension recordings, fluid-induced peristalsis, ET-1 expression, qPCR, western blots, 3-D LSM-immunofluorescence co-labelling studies in LMMP-CM and a postoperative ileus (POI) model of intestinal inflammation.

KEY RESULTS

In the muscularis externa ETB receptor is expressed exclusively in glia. ET-1 is expressed in RiboTag (ChAT)-neurons, isolated ganglia and intra-ganglionic varicose-nerve fibres co-labelled with peripherin or SP. ET-1 release provides activity-dependent glial ETB receptor modulation of Ca2+ waves in neural evoked glial responses. BQ788 reveals amplification of glial and neuronal Ca2+ responses and excitatory cholinergic contractions, sensitive to L-NAME. Gliotoxins disrupt SaTX-induced glial-Ca2+ waves and prevent BQ788 amplification of contractions. The ETB receptor is linked to inhibition of contractions and peristalsis. Inflammation causes glial ETB up-regulation, SaTX-hypersensitivity and glial amplification of ETB signalling. In vivo BQ788 (i.p., 1 mg·kg-1 ) attenuates intestinal inflammation in POI.

CONCLUSION AND IMPLICATIONS

Enteric glial ET-1/ETB signalling provides dual modulation of neural-motor circuits to inhibit motility. It inhibits excitatory cholinergic and stimulates inhibitory nitrergic motor pathways. Amplification of glial ETB receptors is linked to muscularis externa inflammation and possibly pathogenic mechanisms of POI.

Damage-induced NAD release activates intestinal CD4+ and CD8+ T cell via P2X7R signaling

BACKGROUND

Postoperative ileus (POI) is characterized by the activation of inflammation triggered by tissue damage. Damage-associated molecular patterns (DAMPs) reportedly induce local inflammation after injury. However, the impact of DAMPs on intestinal resident lymphocytes during POI remains poorly elucidated.

METHODS

POI in mice was induced via intestinal manipulation (IM). The concentration of nicotinamide adenine dinucleotide (NAD) was detected after IM. The gastrointestinal motility of the mice was assessed after IM or NAD injection. Cytokine production and calcium influx in T cells were investigated after NAD stimulation using flow cytometry.

RESULTS

The concentration of extracellular NAD significantly increased after IM administration, and NAD directly impaired gastrointestinal motility. Intraperitoneal injection of NAD promoted the expression of TNF-α in intestinal CD8+ and CD4+ T cells, but only IFN-γ production by CD8+ T cells was significantly promoted by NAD injection. Granzyme B production in CD8+ and CD4+ T cells decreased after administration. Concordantly, the same results were observed in NAD stimulation of intestinal CD3+ T cells in vitro. Blocking the P2X7R-related membrane enzyme ART2.2 significantly diminished the pro-inflammatory effect of NAD.

CONCLUSION

IM includes the release of NAD derived from damaged tissues, consequently promoting pro-inflammatory cytokine production in intestinal CD4+ and CD8+ T lymphocytes. NAD-induced intestinal T cells activation may be associated with POI progression in the mouse.

Purinergic P2X7 receptor antagonist ameliorates intestinal inflammation in postoperative ileus

Postoperative ileus (POI) is a postsurgical gastrointestinal motility dysfunction caused by mechanical stress to the intestine during abdominal surgery. POI leads to nausea and vomiting reduced patient quality of life, as well as high medical costs and extended hospitalization. Intestinal inflammation caused by macrophages and neutrophils is thought to be important in the mechanism of POI. Surgery-associated tissue injury and inflammation induce the release of adenosine triphosphate (ATP) from injured cells. Released ATP binds the purinergic P2X7 receptor (P2X7R) expressed on inflammatory cells, inducing the secretion of inflammatory mediators. P2X7R antagonists are thought to be important mediators of the first step in the inflammation process, and studies in chemically induced colitis models confirmed that P2X7R antagonists exhibit anti-inflammatory effects. Therefore, we hypothesized that P2X7R plays an important role in POI. POI models were generated from C57BL/6J mice. Mice were treated with P2X7R antagonist A438079 (34 mg/kg) 30 min before and 2 hr after intestinal manipulation (IM). Inflammatory cell infiltration and gastrointestinal transit were measured. A438079 ameliorated macrophage and neutrophil infiltration in the POI model. Impaired intestinal transit improved following A438079 treatment. P2X7R was expressed on both infiltrating and resident macrophages in the inflamed ileal muscle layer. The P2X7R antagonist A438079 exhibits anti-inflammatory effects via P2X7R expressed on macrophages and therefore could be a target in the treatment of POI.

High Hydrostatic Pressure Processing of Human Milk Increases Apelin and GLP-1 Contents to Modulate Gut Contraction and Glucose Metabolism in Mice Compared to Holder Pasteurization

BACKGROUND

High hydrostatic pressure (HHP) processing is a non-thermal method proposed as an alternative to Holder pasteurization (HoP) for the sterilization of human breast milk (BM). HHP preserves numerous milk bioactive factors that are degraded by HoP, but no data are available for milk apelin and glucagon-like peptide 1 (GLP-1), two hormones implicated in the control of glucose metabolism directly and via the gut-brain axis. This study aims to determine the effects of HoP and HHP processing on apelin and GLP-1 concentrations in BM and to test the effect of oral treatments with HoP- and HHP-BM on intestinal contractions and glucose metabolism in adult mice.

METHODS

Mice were treated by daily oral gavages with HoP- or HHP-BM during one week before intestinal contractions, and glucose tolerance was assessed. mRNA expression of enteric neuronal enzymes known to control intestinal contraction was measured.

RESULTS

HoP-BM displayed a reduced concentration of apelin and GLP-1, whereas HHP processing preserved these hormones close to their initial levels in raw milk. Chronic HHP-BM administration to mice increased ileal mRNA nNos expression level leading to a decrease in gut contraction associated with improved glucose tolerance.

CONCLUSION

In comparison to HoP, HPP processing of BM preserves both apelin and GLP-1 and improves glucose tolerance by acting on gut contractions. This study reinforces previous findings demonstrating that HHP processing provides BM with a higher biological value than BM treated by HoP.

Steroid Receptor Coactivator-3 Is Required for Inhibition of the Intestinal Muscularis Inflammatory Response of Postoperative Ileus in Mice

Inflammation theory has suggested that the pathogenesis of postoperative ileus (POI) involves the steroid receptor coactivator-3 (SRC-3). Therefore, we investigated the role of SRC-3 in the muscles of the small intestine using a mouse POI model. Here, we reported that intestinal manipulation (IM) significantly reduced the extent of phenol red migration in the entire gastrointestinal tract, and the calculated geometric center (GC) value in wild-type (WT) mice at 24 h after surgery was higher than that in the knockout (KO) mice and in the sham-operated control group. The expression of SRC-3 was upregulated in the mouse intestinal muscularis at 24 h after surgical manipulation, and the mRNA and protein levels of inflammatory cytokines were upregulated compared with those in the control group. At 24 h after IM, the number of neutrophils in the experimental group was significantly higher than that in the control group; in the IM group, the number of neutrophils in the SRC-3-/- mice was markedly higher than that in the WT mice. At 24 h after IM, the myeloperoxidase (MPO) activity in the experimental group was significantly higher than that in the control group. In the IM group, the MPO activity of the SRC-3-/- mice was markedly higher than that of the WT mice. In summary, proinflammatory cytokines, the number of neutrophils, and the MPO activity were significantly increased in the muscularis of the jejunum and ileum of KO mice after IM compared with those of the WT mice, indicating that SRC-3 might play a protective role in POI.

Fingerprinting Acute Digestive Diseases by Untargeted NMR Based Metabolomics

Precision medicine may significantly contribute to rapid disease diagnosis and targeted therapy, but relies on the availability of detailed, subject specific, clinical information. Proton nuclear magnetic resonance (¹H–NMR) spectroscopy of body fluids can extract individual metabolic fingerprints. Herein, we studied 64 patients admitted to the Florence main hospital emergency room with severe abdominal pain. A blood sample was drawn from each patient at admission, and the corresponding sera underwent ¹H–NMR metabolomics fingerprinting. Unsupervised Principal Component Analysis (PCA) analysis showed a significant discrimination between a group of patients with symptoms of upper abdominal pain and a second group consisting of patients with diffuse abdominal/intestinal pain. Prompted by this observation, supervised statistical analysis (Orthogonal Partial Least Squares–Discriminant Analysis (OPLS-DA)) showed a very good discrimination (>90%) between the two groups of symptoms. This is a surprising finding, given that neither of the two symptoms points directly to a specific disease among those studied here. Actually herein, upper abdominal pain may result from either symptomatic gallstones, cholecystitis, or pancreatitis, while diffuse abdominal/intestinal pain may result from either intestinal ischemia, strangulated obstruction, or mechanical obstruction. Although limited by the small number of samples from each of these six conditions, discrimination of these diseases was attempted. In the first symptom group, >70% discrimination accuracy was obtained among symptomatic gallstones, pancreatitis, and cholecystitis, while for the second symptom group >85% classification accuracy was obtained for intestinal ischemia, strangulated obstruction, and mechanical obstruction. No single metabolite stands up as a possible biomarker for any of these diseases, while the contribution of the whole ¹H–NMR serum fingerprint seems to be a promising candidate, to be confirmed on larger cohorts, as a first-line discriminator for these diseases.

Intestinal manipulation affects mucosal antimicrobial defense in a mouse model of postoperative ileus

Aim

To explore the effects of abdominal surgery and interleukin-1 signaling on antimicrobial defense in a model of postoperative ileus.

Methods

C57BL/6 and Interleukin-1 receptor type I (IL-1R1) deficient mice underwent intestinal manipulation to induce POI. Expression of mucosal IL-1α, IL-1β and IL-1R1 and several antimicrobial peptides and enzymes were measured by quantitative PCR or ELISA, western blotting or immunohistochemistry. Bacterial overgrowth was determined by fluorescent in-situ hybridization and counting of jejunal luminal bacteria. Translocation of aerobic and anaerobic bacteria into the intestinal wall, mesenteric lymph nodes, liver and spleen was determined by counting bacterial colonies on agar plates 48h after plating of tissue homogenates. Antimicrobial activity against E. coli and B. vulgatus was analyzed in total and cationic fractions of small bowel mucosal tissue homogenates by a flow cytometry-based bacterial depolarization assay.

Results

Jejunal bacterial overgrowth was detected 24h after surgery. At the same time point, but not in the early phase 3h after surgery, bacterial translocation into the liver and mesenteric lymph nodes was observed. Increased antimicrobial activity against E. coli was induced within early phase of POI. Basal antimicrobial peptide and enzyme gene expression was higher in the ileal compared to the jejunal mucosa. The expression of lysozyme 1, cryptdin 1, cryptdin 4 and mucin 2 were reduced 24h after surgery in the ileal mucosa and mucin 2 was also reduced in the jejunum. Postoperative IL-1α and IL-1β were increased in the postoperative mucosa. Deficiency of IL-1R1 affected the expression of antimicrobial peptides during homeostasis and POI.

Conclusion

Small bowel antimicrobial capacity is disturbed during POI which is accompanied by bacterial overgrowth and translocation. IL-1R1 is partially involved in the gene expression of mucosal antimicrobial peptides. Altered small bowel antimicrobial activity may contribute also to POI development and manifestation in patients undergoing abdominal surgery.

Surgical intestinal manipulation increases gene expression of TrkA, CGRP, and PAR-2 IN dorsal root ganglia in the rat

BACKGROUND

Surgical handling of the bowel evokes degranulation of peritoneal mast cells (PMC). Nonetheless, role of PMCs in postoperative ileus (POI) is somewhat controversial. We aimed to investigate if intestinal manipulation elicits changes in afferent mediators related to MC activation and alteration of gastrointestinal (GI) motility.

METHODS

Postoperative ileus was induced by intestinal manipulation in Sprague-Dawley rats. Additionally, compound 48/80 (C48/80) and ketotifen were used to modulate MC activity. Rat mast cell protease 6 (RMCP-6, ELISA) release was determined in peritoneal lavage 20 min after intestinal manipulation. At 24 h, GI transit was determined. Gene expression of calcitonin gene-related peptide (CGRP), protease-activated receptor-2 (PAR-2), nerve growth factor (NGF), and TrkA receptor was determined (PCR) in dorsal root ganglia (DRG). Ileal wall inflammation was assessed by myeloperoxidase (MPO) activity, interleukin-6 expression (IL-6).

KEY RESULTS

Intestinal manipulation and exposure to C48/80-induced degranulation of PMCs delayed GI transit and up-regulated IL-6 and MPO activity. Intestinal manipulation, but not C48/80, up-regulated CGRP, PAR-2, and NGF/TrkA in DRGs. Ketotifen only improved gastric emptying and fecal output. Up-regulation of CGRP and TrkA expression in DRG was not prevented by ketotifen.

CONCLUSIONS & INFERENCES

Postoperative ileus is accompanied by activation of CGRP, NGF-TrkA, and PAR-2 in DRGs. Our results suggest that these mediators could be a target in further POI studies in order to find new therapeutic targets for this medical condition.

Effect of Tributyrin on Electrical Activity in the Small Intestine during Early Postoperative Period

The effect of enteral administration of tributyrin on electrical activity in the upper segments of the small intestine was examined in rats on the model of postoperative ileus. This postoperative state is characterized with pronounced and long-term disturbances in generation of migrating myoelectric complex of the small intestine. The enteral administration of tributyrin in the early postoperative period aimed to suppress the non-adrenergic non-cholinergic influences and activation of the cholinergic anti-inflammatory pathways is an effective procedure to normalize the migrating myoelectric complex and therefore the coordinated propulsive peristalsis in the small intestine.

Protective effect of exogenous nitrite in postoperative ileus

BACKGROUND AND PURPOSE

As the pathogenesis of postoperative ileus (POI) involves inflammation and oxidative stress, comparable to ischaemia/reperfusion injury which can be ameliorated with nitrite, we investigated whether nitrite can protect against POI and explored the mechanisms involved.

EXPERIMENTAL APPROACH

We used intestinal manipulation (IM) of the small intestine to induce POI in C57BL/6J mice. Sodium nitrite (48 nmol) was administered intravenously just before IM. Intestinal transit was assessed using fluorescent imaging. Bethanechol-stimulated jejunal circular muscle contractions were measured in organ baths. Inflammatory parameters, neutrophil infiltration, inducible NOS (iNOS) activity, reactive oxygen species (ROS) levels, mitochondrial complex I activity and cGMP were measured in the intestinal muscularis.

KEY RESULTS

Pre-treatment with nitrite markedly improved the delay in intestinal transit and restored the reduced intestinal contractility observed 24 h following IM. This was accompanied by reduced protein levels of TNF-α, IL-6 and the chemokine CCL2, along with reduced iNOS activity and ROS levels. The associated neutrophil influx at 24 h was not influenced by nitrite. IM reduced mitochondrial complex I activity and cGMP levels; treatment with nitrite increased cGMP levels. Pre-treatment with the NO scavenger carboxy-PTIO or the soluble guanylyl cyclase inhibitor ODQ abolished nitrite-induced protective effects.

CONCLUSIONS AND IMPLICATIONS

Exogenous nitrite deserves further investigation as a possible treatment for POI. Nitrite-induced protection of POI in mice was dependent on NO and this effect was not related to inhibition of mitochondrial complex I, but did involve activation of soluble guanylyl cyclase.

Therapeutic action of 5-HT3 receptor antagonists targeting peritoneal macrophages in post-operative ileus

BACKGROUND AND PURPOSE

Post-operative ileus (POI) is induced by intestinal inflammation. Here, we aimed to clarify the effects of 5-HT3 receptor antagonists against POI.

EXPERIMENTAL APPROACH

We administered three 5-HT3 receptor antagonists, ondansetron, tropisetron and palonosetron, to a mouse model of POI induced by surgical intestinal manipulation (IM). Immunohistochemistry, intestinal transit, inflammatory mediator mRNA expression and 5-HT content were measured. In some experiments, 5-HT3 A receptor null mice were used.

KEY RESULTS

Three 5-HT3 receptor antagonists reduced IM-induced infiltration of inflammatory CD68-positive macrophages and myeloperoxidase-stained neutrophils. Ondansetron exhibited no anti-inflammatory actions in 5-HT3 A receptor null mice. Ondansetron inhibited expression of the chemokine CCL2, IL-1β, IL-6, TNF-α and iNOS mRNAs up-regulated by IM, and also ameliorated the delayed gastrointestinal transit. Peritoneal macrophages, but not most infiltrating monocyte-derived macrophages, expressed 5-HT3 receptors. IM stimulation increased the 5-HT content of peritoneal lavage fluid, which up-regulated mRNA expression of proinflammatory cytokines in peritoneal macrophages. Immunohistochemical localization of 5-HT3 receptors suggests that ondansetron suppressed expression of these mRNAs in activated peritoneal macrophages, adhering to the serosal region of the inflamed intestinal wall.

CONCLUSION AND IMPLICATIONS

5-HT3 receptor antagonists were anti-inflammatory, mainly targeting peritoneal macrophages expressing these receptors. They also restored the delayed gastrointestinal transit by IM. 5-HT3 receptor antagonists should be therapeutically useful agents against POI.

[Prognostication and prophylaxis of the adhesions recurrence postoperatively in patients suffering acute adhesive peritoneal disease complicated by ileus]

The results of treatment of 92 patients, suffering an acute ileus, were analyzed. After urgent operative interventions for an acute ileus the recurrence have occurred in 19.6% patients. To reduce the operative intervention traumaticity the preference was given to local viscerolysis conduction. For the adhesions occurrence prophylaxis a barrier medicines were used, what have promoted the reduction of contents of a connective tissue metabolites, excluding oxyprolin, concentration of which have exceeded such in a control, what have guaranteed the risk lowering for postoperative adhesions occurrence.

[Evaluation of intestinal viability on a simulation model of a small ileus based on determination of dielectric parameters]

Interrelationship between dielectric parameters and level of ATPH before and during ischemia, as well as with indices of survival after elimination of strangulation, was estimated on a simulation model of strangulation ileus in rats. The data obtained permit to suppose, that parameter tg δm may be used as effective noninvasive criterion of diagnosis in real time for estimation of the intestinal wall state in strangulation. Resection of the infringed intestine without elimination of strangulation is necessary in tg δm less than 2.20, in tg δm more than 2.36 the elimination of infringement is indicated, because there exist possibility to restore intestinal function after ischemic-reperfusion injury. Tactics of treatment in intermediate meanings of tg δm is not determined, but its measurement before reperfusion may help in estimation of a small intestine viability and choice of surgical tactics in its ischemia.

Brain peptides and the modulation of postoperative gastric ileus

Postoperative ileus (POI) develops after abdominal surgery irrespective of the site of surgery. When prolonged, POI can lead to longer hospitalization times and higher healthcare costs. Moreover, it is associated with complaints for the patient. In order to develop new strategies to treat this condition, a deeper understanding of the pathophysiology of the POI is necessary. This review will focus on brain peptides (ghrelin, nesfatin-1, somatostatin, corticotropin-releasing factor, thyrotropin-releasing hormone and calcitonin gene-related peptide) involved in the mediation of POI and the possible modulation of these pathways to shorten the time of POI. Lastly, the role of vagal signaling or chewing gum as potential treatment strategies of alleviating symptoms of POI is discussed.

Mast cells play no role in the pathogenesis of postoperative ileus induced by intestinal manipulation

Introduction

Intestinal manipulation (IM) during abdominal surgery results in intestinal inflammation leading to hypomotility or ileus. Mast cell activation is thought to play a crucial role in the pathophysiology of postoperative ileus (POI). However, this conclusion was mainly drawn using mast cell-deficient mouse models with abnormal Kit signaling. These mice also lack interstitial cells of Cajal (ICC) resulting in aberrant gastrointestinal motility even prior to surgery, compromising their use as model to study POI. To avoid these experimental weaknesses we took advantage of a newly developed knock-in mouse model, Cpa3^Cre/+, devoid of mast cells but with intact Kit signaling.

Design

The role of mast cells in the development of POI and intestinal inflammation was evaluated assessing gastrointestinal transit and muscularis externa inflammation after IM in two strains of mice lacking mast cells, i.e. Kit^W-sh/W-sh and Cpa3^Cre/+ mice, and by use of the mast cell stabilizer cromolyn.

Results

Kit^W-sh/W-sh mice lack ICC networks and already revealed significantly delayed gastrointestinal transit even before surgery. IM did not further delay intestinal transit, but induced infiltration of myeloperoxidase positive cells, expression of inflammatory cytokines and recruitment of monocytes and neutrophils into the muscularis externa. On the contrary, Cpa3^Cre/+ mice have a normal network of ICC and normal gastrointestinal. Surprisingly, IM in Cpa3^Cre/+ mice caused delay in gut motility and intestinal inflammation as in wild type littermates mice (Cpa3^+/+). Furthermore, treatment with the mast cell inhibitor cromolyn resulted in an inhibition of mast cells without preventing POI.

Conclusions

Here, we confirm that IM induced mast cell degranulation. However, our data demonstrate that mast cells are not required for the pathogenesis of POI in mice. Although there might be species differences between mouse and human, our results argue against mast cell inhibitors as a therapeutic approach to shorten POI.

Peritoneal air exposure elicits an intestinal inflammation resulting in postoperative ileus

BACKGROUND

The pathogenesis of postoperative ileus (POI) is complex. The present study was designed to investigate the effects of peritoneal air exposure on the POI intestinal inflammation and the underlying mechanism.

METHODS

Sprague-Dawley rats were randomized into five groups (6/group): the control group, the sham group, and three exposure groups with peritoneal air exposure for 1, 2, or 3 h. At 24 h after surgery, we analyzed the gastrointestinal transit, the serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-10, the myeloperoxidase activity, and the levels of TNF-α, IL-1β, IL-6, and IL-10 in the ileum and colon. The oxidant and antioxidant levels in the ileum and colon were analyzed by measuring malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC).

RESULTS

Peritoneal air exposure caused an air-exposure-time-dependent decrease in the gastrointestinal transit. The length of peritoneal air exposure is correlated with the severity of both systemic and intestinal inflammations and the increases in the levels of MDA, SOD, GSH-Px, and T-AOC.

CONCLUSIONS

The length of peritoneal air exposure is proportional to the degree of intestinal paralysis and the severity of intestinal inflammation, which is linked to the oxidative stress response.

The dual effect of cannabinoid receptor-1 deficiency on the murine postoperative ileus

Introduction

Intestinal inflammatory responses play a critical role in the pathogenesis of postoperative ileus (POI). As cannabinoid receptor-1 (CB1) is involved in inhibiting gastrointestinal (GI) motility and anti-inflammation, we aimed to explore its contribution to POI.

Methods

Experimental POI was induced in adult female CB1-deficient (CB1–/–) mice and wild-type littermates (C57BL/6N) by standardized small bowel manipulation. Twenty-four hours after surgery, GI transit was assessed by charcoal transport. FITC avidin, F4/80, and myeloperoxidase immunohistochemistry techniques were used to evaluate the inflammatory response in the muscularis of ileum and colon. Expressions of p38MAPK and its phosphorylated form (pp38) in the intestine were determined. Plasma levels of proinflammatory cytokines and chemokines were measured by ELISA as well.

Results

POI was characterized by decreased GI transit (p<0.01) and accompanied by a marked intestinal and systematic inflammatory response in wild-type and CB1–/– mice. Increased numbers of inflammatory cells, including macrophages, neutrophils, and mast cells were observed in the muscularis of ileum and colon (p<0.01, or p<0.05). Plasma levels of interleukin-6 (IL-6), cytokine-induced neutrophil chemoattractant-1 (CINC-1/KC), and monocyte chemoattractant protein-1 (MCP-1) were elevated (p<0.01, or p<0.05). Expression of p38 and pp38 increased in the intestine (p<0.01, or p<0.05). CB1–/– mice showed an increased inflammatory response during POI, especially the systemic inflammatory markers, such as IL-6, KC, CINC1, and pp38 expression were increased as compared to those in WT mice (p<0.05).

Conclusions

Intestinal motility was inhibited during POI. In this condition, inhibition of motility did not seem to be altered by the absence of CB1 receptors, however, an increased inflammatory response was observed in CB1–/– mice. Hence, CB1 receptor activation rather than inhibition may reduce the inflammatory response in POI, which has a remote potential to relate into reduced inhibition of intestinal motility during POI.

Ghrelin as a target for gastrointestinal motility disorders

The therapeutic potential of ghrelin and synthetic ghrelin receptor (GRLN-R) agonists for the treatment of gastrointestinal (GI) motility disorders is based on their ability to stimulate coordinated patterns of propulsive GI motility. This review focuses on the latest findings that support the therapeutic potential of GRLN-R agonists for the treatment of GI motility disorders. The review highlights the preclinical and clinical prokinetic effects of ghrelin and a series of novel ghrelin mimetics to exert prokinetic effects on the GI tract. We build upon a series of excellent reviews to critically discuss the evidence that supports the potential of GRLN-R agonists to normalize GI motility in patients with GI hypomotility disorders such as gastroparesis, post-operative ileus (POI), idiopathic chronic constipation and functional bowel disorders.

Gastrointestinal dysfunction in mice with a targeted mutation in the gene encoding vasoactive intestinal polypeptide: a model for the study of intestinal ileus and Hirschsprung's disease

In 1970, Drs. Said and Mutt isolated a novel peptide from porcine intestinal extracts with powerful vasoactive properties, and named it vasoactive intestinal peptide (VIP). Since then, the biological actions of VIP in the gut as well as its signal transduction pathways have been extensively studied. A variety of in vitro and in vivo studies have indicated that VIP, expressed in intrinsic non-adrenergic non-cholinergic (NANC) neurons, is a potent regulator of gastrointestinal (GI) motility, water absorption and ion flux, mucus secretion and immune homeostasis. These VIP actions are believed to be mediated mainly by interactions with highly expressed VPAC(1) receptors and the production of nitric oxide (NO). Furthermore, VIP has been implicated in numerous physiopathological conditions affecting the human gut, including pancreatic endocrine tumors secreting VIP (VIPomas), insulin-dependent diabetes, Hirschsprung's disease, and inflammatory bowel syndromes such as Crohn's disease and ulcerative colitis. To further understand the physiological roles of VIP on the GI tract, we have begun to analyze the anatomical and physiological phenotype of C57BL/6 mice lacking the VIP gene. Herein, we demonstrate that the overall intestinal morphology and light microscopic structure is significantly altered in VIP(-/-) mice. Macroscopically there is an overall increase in weight, and decrease in length of the bowel compared to wild type (WT) controls. Microscopically, the phenotype was characterized by thickening of smooth muscle layers, increased villi length, and higher abundance of goblet cells. Alcian blue staining indicated that the latter cells were deficient in mucus secretion in VIP(-/-) mice. The differences became more pronounced from the duodenum to the distal jejunum or ileum of the small bowel but, became much less apparent or absent in the colon with the exception of mucus secretion defects. Further examination of the small intestine revealed larger axonal trunks and unusual unstained patches in myenteric plexus. Physiologically, the VIP(-/-) mice showed an impairment in intestinal transit. Moreover, unlike WT C57BL/6 mice, a significant percentage of VIP(-/-) mice died in the first postnatal year with overt stenosis of the gut.

The effect of epidural analgesia on postoperative outcome after colorectal surgery

OBJECTIVE

The aim of this review was to determine the effects of epidural analgesia as it relates to outcome after colorectal surgery.

METHOD

We searched and reviewed studies that included colorectal surgery and epidural method of analgesia listed on the Pubmed, Medline, Embase and the Cochrane library database.

RESULTS

The majority of data demonstrate a superior effect of epidural analgesia on pain control after colorectal surgery. Well designed randomized controlled trials (RCT's) have also shown that epidural analgesia reduces the duration of ileus after colorectal surgery. Limited data suggest the additional benefit may be minimal after laparoscopic surgery or when epidural analgesia is used as part of a multimodal regime. Data does not convincingly show either a clear harmful or beneficial effect of epidural analgesia on rates of anastomotic leakage. Epidural analgesia may have beneficial effects on postoperative lung function, however due to low numbers, the effects on cardiovascular and thromboembolic complications are indeterminate. Length of hospital stay has not been shown to be shortened by sole use of an epidural and, although epidural analgesia may be apparently more costly, alternatives may incur higher indirect costs and decreased patient satisfaction.

CONCLUSION

Randomized controlled trials have shown a benefit for epidurals on postoperative pain relief, and ileus, and possibly respiratory complications. There is no proven benefit with regard to length of stay. There are a number of unresolved issues which further focussed RCT's may help clarify such as effects of epidural on complication rates after colorectal surgery.

Altered inflammatory gene expression underlies increased susceptibility to murine postoperative ileus with advancing age

Susceptibility to postoperative ileus following abdominal surgery increases with advancing age. The mechanisms underlying this phenomenon are unknown. This study compares functional and molecular endpoints between young-adult (2 mo old), middle-aged (15 mo old), and elderly mice (26-30 mo old) to identify potential mechanisms. Susceptibility to ileus was assessed by measuring gastrointestinal transit (geometric center) 24 h after anesthesia, laparotomy, and light manipulation (LM) of the small bowel. Proinflammatory (IL-6, COX-2, inducible nitric oxide synthase) and anti-inflammatory (IL-10, heme oxygenase-1) gene and protein expressions were determined by real time RT-PCR, Western blot, and ELISA. LM did not alter gastrointestinal transit in young animals (geometric center = 8.8 +/- 0.9), but transit was increasingly delayed in middle-aged (6.9 +/- 0.8, P = 0.03) and elderly animals (4.7 +/- 0.6, P = 0.013). Despite the lack of LM effect on transit in young mice, IL-6 and COX-2 mRNA expressions were significantly increased postoperatively (165 +/- 24-fold and 2.9 +/- 0.3-fold, respectively). Expressions were increased further in middle-aged mice (1,103 +/- 187-fold; 4.4 +/- 0.7-fold) and further still in elderly mice (1,218 +/- 168-fold; 6.9 +/- 0.3-fold). IL-10 and heme oxygenase-1 gene expressions were also elevated postoperatively in young mice (4.8 +/- 0.5-fold and 13.0 +/- 1.3-fold, respectively) and were further increased in middle-aged mice (7.5 +/- 0.6-fold; 21.8 +/- 3.2-fold). However, inductions in elderly mice were significantly blunted (5.8 +/- 0.9-fold; 16.9 +/- 0.8-fold). There is both an age-dependent increase in the proinflammatory mediator expression and an age-dependent decrease in anti-inflammatory mediator expressions following minor insult to the bowel. Such imbalances between pro- and anti-inflammatory mechanisms may form the basis for increased susceptibility to ileus and for the increased severity and duration of ileus observed in the elderly.

Lymphoid follicles of the ileal Peyer's patch of lambs express low levels of PrP, as demonstrated by quantitative real-time RT-PCR on microdissected tissue compartments, in situ hybridization and immunohistochemistry

The expression level of normal cellular prion protein (PrPC) is thought to influence the transmission of transmissible spongiform encephalopathies (TSEs) from the peripheral entry site to the site of pathological changes in the central nervous system. In many TSEs, the clinical disease is preceded by a period in which the agent accumulates in lymphoid organs, particularly in association with follicular dendritic cells of lymphoid follicles. As the probable route of entry of the TSE agent is via the gut, the expression profile of PrP was examined in well-developed gut-associated lymphoid tissue of lambs, the ileal Peyer's patch, by laser microdissection and real-time RT-PCR. Lymphoid follicles were found to have very low levels of expression, whilst highest levels were detected in the outer submucosa and the muscular layer. These findings were supported by in situ hybridization and immunohistochemistry, which showed specific labelling in nerve cells in ganglia of the submucosal (Meissner's) and myenteric (Auerbach's) plexi of the enteric nervous system. Based on the assumption that potential sites for conversion to the scrapie-related prion protein (PrPSc) should display high levels of expression of PrPC, this study suggests that the accumulation of PrPSc in the lymphoid follicles of the Peyer's patch is not preceded by PrP conversion in the same tissue compartment.

Hypertonic saline resuscitation prevents hydrostatically induced intestinal edema and ileus

OBJECTIVE

We have shown that acute edema induced by mesenteric venous hypertension (MV-HTN) impairs intestinal transit and reduces the standardized engineering measures of intestinal stiffness (elastic modulus) and residual stress (opening angle). We hypothesized that hypertonic saline (7.5%) would reverse these detrimental effects of acute edema.

DESIGN

Laboratory study.

SETTING

University laboratory.

SUBJECTS

Male Sprague Dawley rats (270-330 g).

INTERVENTIONS

Rats were randomized to five groups: sham, MV-HTN alone, MV-HTN with 4 mL/kg normal saline resuscitation (equal volume), MV-HTN with 33 mL/kg normal saline resuscitation (equal salt), and MV-HTN with 4 mL/kg hypertonic saline. Intestinal edema was measured by wet to dry tissue weight ratio. A duodenal catheter was placed and, 30 mins before death, fluorescein isothiocyanate Dextran was injected. At death, dye concentrations were measured to determine intestinal transit. Segments of distal ileum were hung to a fixed point in a tissue bath and to a force displacement transducer and stretched in increments of 1 mm; we recorded the new length and the corresponding force from the force displacement transducer to determine elastic modulus. Next, two transverse cuts were made yielding a 1- to 2-mm thick ring-shaped segment of tissue which was then cut radially to open the ring. Then the opening angle was measured.

MEASUREMENTS AND MAIN RESULTS

MV-HTN, MV-HTN with 4 mL/kg normal saline, and MV-HTN with 33 mL/kg normal saline caused a significant increase in tissue edema and a significant decrease in intestinal transit, stiffness, and residual stress compared with sham. Hypertonic saline significantly lessened the effect of edema on intestinal transit and prevented the changes in stiffness and residual stress.

CONCLUSIONS

Hypertonic saline prevented intestinal tissue edema. In addition, hypertonic saline improved intestinal transit, possibly through more efficient transmission of muscle force through stiffer intestinal tissue.

[Estimation of efficiency of complex-method intestinal therapy using Nitella flexilis test-object for acute intestinal obstruction of various etiology]

The aim of our investigation was to define the presence of correlation between toxicity of intestinal contents and clinical and laboratory indices in the cases of ileus and peritonitis with the use of complex method of enteral therapy. Experiments have been carried out on internodal cells of Nitella Flexilis water plant. Efficiency of the given method (investigation of toxicity of the intestinal content with the use of test-object Nitella Flexilis) has been studied in 25 patients, who underwent correction of morpho-functional status of small intestine. Results of investigation have shown that changes in toxicity of intestinal content reliably reflect the nature and dynamics of the pathobiologic processes proceeding in GIS in treated patients suffering from acute intestinal impassability. Using the method of correction of morpho-functional status of small intestine decreases the role of "Intestinal factor" in formation of endogenous intoxication, which in turn results in early normalization of clinical and laboratory indices, favored process of early post-operational period, decreased rate of lethality and shortened rehabilitation period.

Mast cell degranulation during abdominal surgery initiates postoperative ileus in mice

BACKGROUND & AIMS

Inflammation of the intestinal muscularis following manipulation during surgery plays a crucial role in the pathogenesis of postoperative ileus. Here, we evaluate the role of mast cell activation in the recruitment of infiltrates in a murine model.

METHODS

Twenty-four hours after control laparotomy or intestinal manipulation, gastric emptying was determined. Mast cell degranulation was determined by measurement of mast cell protease-I in peritoneal fluid. Intestinal inflammation was assessed by determination of tissue myeloperoxidase activity and histochemical staining.

RESULTS

Intestinal manipulation elicited a significant increase in mast cell protease-I levels in peritoneal fluid and resulted in recruitment of inflammatory infiltrates to the intestinal muscularis. This infiltrate was associated with a delay in gastric emptying 24 hours after surgery. Pretreatment with mast cell stabilizers ketotifen (1 mg/kg, p.o.) or doxantrazole (5 mg/kg, i.p.) prevented both manipulation-induced inflammation and gastroparesis. Reciprocally, in vivo exposure of an ileal loop to the mast cell secretagogue compound 48/80 (0.2 mg/mL for 1 minute) induced muscular inflammation and delayed gastric emptying. The manipulation-induced inflammation was dependent on the presence of mast cells because intestinal manipulation in mast cell-deficient Kit/Kitv mice did not elicit significant leukocyte recruitment. Reconstitution of Kit/Kitv mice with cultured bone marrow-derived mast cells from congenic wild types restored the manipulation-induced inflammation.

CONCLUSIONS

Our results show that degranulation of connective tissue mast cells is a key event for the establishment of the intestinal infiltrate that mediates postoperative ileus following abdominal surgery.

Intestinal wall damage in simple ileus in rabbits: immune-modulator role of somatostatin

BACKGROUND/AIMS

We aim to determine in which way the local immune system would be responsible for the structural changes in intestinal obstruction, and how these are influenced by Somatostatin, an intestinal peptide with immunomodulatory properties. Simple ileus causes a series of functional and anatomical changes, which have been related to the peptidergic neural system, and inflammatory mediators. These changes are reversible with the use of Somatostatin.

METHODOLOGY

27 rabbits divided into three groups, were subjected to the same procedure, in which a simple closed loop obstruction is caused by means of jejunum ligatures. The three groups are perfused with physiologic saline during 24 hours post-obstruction; one of them is perfused with Somatostatin from the time of intervention, and other after 8 hours. Samples of the intestinal wall are taken for histological analysis, and of the intraluminal liquid to determine the tumor necrosis factor alpha, interleukin 2, interleukin 6, and serotonin.

RESULTS

Both group treated with Somatostatin show a wall which is in good condition, while the untreated group showed lesions. These lesions are related to higher levels of tumor necrosis factor alpha, and interleukin 2, while there were no changes in the levels of interleukin 6.

CONCLUSIONS

The Somatostatin in perfusion shows a cytoprotective activity in the intestinal wall, and a blockage of the production of mediators of cellular immunity, while humoral immunity does not appear to be involved in these phenomena.

Two new peptides to improve post-operative gastric ileus in dog

Peptides can influence gastrointestinal motility, and from data obtained earlier in rats, we hypothesized that MTL-RP/Ghrelin, as well as CGRP receptor antagonist 8-37, could improve gastric post-operative ileus in dog. Dogs submitted to laparotomy were perfused with or saline or CGRP 8-37 or MTL-RP/Ghrelin on days 1-4 post-operatively while gastric emptying was estimated by measuring the postprandial increase in plasma acetaminophen ingested with a meal. As expected, in saline-treated animals the gastric emptying function was impaired post-operatively. The total amount of acetaminophen emptied (AUC over 150 min) on post-operative days 1-4 reached respectively 31+/-5%, 65+/-8%, 60+/-8% and 62+/-8% of the normal emptying capacity. CGRP antagonist increased the total emptying of acetaminophen to 52+/-5% on day 1, 95+/-2% on day 2 and 103+/-3% (P<0.05) on day 3. The delayed emptying of acetaminophen seen post-operatively in saline-treated animals could be completely reversed by MTL-RP/Ghrelin (P<0.01) whether it was given at 100 microg/kg on day 2 (102+/-7% of the normal emptying capacity), 4 microg/kg on day 3 (106+/-7%) or 20 microg/kg on day 4 (132+/-8%). As found earlier in rodents, CGRP receptor antagonist 8-37 as well as MTL-RP/Ghrelin are potent prokinetics to improve post-operative gastric ileus in dog.