Effects of inflammation and/or infection on the neuroendocrine control of fish intestinal motility: A review

Food is the largest expense in fish farms. On the other hand, the fish health and wellbeing are determining factors in aquaculture production where nutrition is a vital process for growing animals. In fact, it is important to remember that digestion and nutrition are crucial for animals' physiology. However, digestion is a very complex process in which food is processed to obtain necessary nutrients and central mechanisms of this process require both endocrine and neuronal regulation. In this context, intestinal motility is essential for the absorption of the nutrients (digestive process determining nutrition). An imbalance in the intestinal motility due to an inadequate diet or an infectious process could result in a lower use of the food and inefficiency in obtaining nutrients from food. Very frequently, farmed fish are infected with different pathogenic microorganism and this situation could alter gastrointestinal physiology and, indirectly reduce fish growth. For these reasons, the present review focuses on analysing how different inflammatory molecules or infections can alter conventional modulators of fish intestinal motility.

G protein-coupled estrogen receptor in colon function, immune regulation and carcinogenesis

Estrogens play important roles in the development and progression of multiple tumor types. Accumulating evidence points to the significance of estrogen action not only in tumors of hormonally regulated tissues such as the breast, endometrium and ovary, but also in the development of colorectal cancer (CRC). The effects of estrogens in physiological and pathophysiological conditions are mediated by the nuclear estrogen receptors α and β, as well as the membrane-bound G protein-coupled estrogen receptor (GPER). The roles of GPER in CRC development and progression, however, remain poorly understood. Studies on the functions of GPER in the colon have shown that this estrogen receptor regulates colonic motility as well as immune responses in CRC-associated diseases, such as Crohn’s disease and ulcerative colitis. GPER is also involved in cell cycle regulation, endoplasmic reticulum stress, proliferation, apoptosis, vascularization, cell migration, and the regulation of fatty acid and estrogen metabolism in CRC cells. Thus, multiple lines of evidence suggest that GPER may play an important role in colorectal carcinogenesis. In this review, we present the current state of knowledge regarding the contribution of GPER to colon function and CRC.

Berberine prevents stress-induced gut inflammation and visceral hypersensitivity and reduces intestinal motility in rats

BACKGROUND

Irritable bowel syndrome (IBS) is a common chronic non-organic disease of the digestive system. Berberine (BBR) has been used to treat patients with IBS, but the underlying therapeutic mechanism is little understood. We believe that BBR achieves its therapeutic effect on IBS by preventing stress intestinal inflammation and visceral hypersensitivity and reducing bowel motility.

AIM

To test the hypothesis that BBR achieves its therapeutic effect on IBS by preventing subclinical inflammation of the intestinal mucosa and reducing visceral hypersensitivity and intestinal motility.

METHODS

IBS was induced in rats via water avoidance stress (WAS). qRT-PCR and histological analyses were used to evaluate the levels of cytokines and mucosal inflammation, respectively. Modified ELISA and qRT-PCR were used to evaluate the nuclear factor kappa-B (NF-κB) signal transduction pathway. Colorectal distention test, gastrointestinal transit measurement, Western blot, and qRT-PCR were used to analyze visceral sensitivity, intestinal motility, the expression of C-kit (marker of Cajal mesenchymal cells), and the expression of brain derived neurotrophic factor (BDNF) and its receptor TrkB.

RESULTS

WAS led to mucosal inflammation, visceral hyperalgesia, and high intestinal motility. Oral administration of BBR inhibited the NF-κB signal transduction pathway, reduced the expression of pro-inflammatory cytokines [interleukin (IL)-1β, IL-6, interferon-γ, and tumor necrosis factor-α], promoted the expression of anti-inflammatory cytokines (IL-10 and transforming growth factor-β), and improved the terminal ileum tissue inflammation. BBR inhibited the expression of BDNF, TrkB, and C-kit in IBS rats, leading to the reduction of intestinal motility and visceral hypersensitivity. The therapeutic effect of BBR at a high dose (100 mg/kg) was superior to than that of the low-dose (25 mg/kg) group.

CONCLUSION

BBR reduces intestinal mucosal inflammation by inhibiting the intestinal NF-κB signal pathway in the IBS rats. BBR reduces the expression of BDNF, its receptor TrkB, and C-kit. BBR also reduces intestinal motility and visceral sensitivity to achieve its therapeutic effect on IBS.

Muscularis macrophages: Key players in intestinal homeostasis and disease

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Muscularis macrophages densily colonize the outermost layer of the gastrointestinal tract.

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Muscularis macrophages communicate with enteric neurons in a bidirectional matter.

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Muscularis macrophages are tissue-protective but can contribute to disease.

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Current challenges are to decipher therapeutic potentials of muscularis macrophages.

Macrophages residing in the muscularis externa of the gastrointestinal tract are highly specialized cells that are essential for tissue homeostasis during steady-state conditions as well as during disease. They are characterized by their unique protective functional phenotype that is undoubtedly a consequence of the reciprocal interaction with their environment, including the enteric nervous system. This muscularis macrophage-neuron interaction dictates intestinal motility and promotes tissue-protection during injury and infection, but can also contribute to tissue damage in gastrointestinal disorders such as post-operative ileus and gastroparesis. Although the importance of muscularis macrophages is clearly recognized, different aspects of these cells remain largely unexplored such their origin, longevity and instructive signals that determine their function and phenotype. In this review, we will discuss the phenotype, functions and origin of muscularis macrophages during steady-state and disease conditions. We will highlight the bidirectional crosstalk with neurons and potential therapeutic strategies that target and manipulate muscularis macrophages to restore their protective signature as a treatment for disease.

[MECHANISMS OF SMALL INTESTINE MOTOR DISORDERS DURING ENDOTOXEMIA AND PATHOPHYSIOLOGICAL RATIONALE FOR THE USE OF TRIBUTYRINE AS ANTI-INFLAMMATORY AND PROKINETIC PHARMACONUTRIENT]

Studying the mechanisms of the small intestine motor function disorders during endotoxemia and searching ways to mitigate them remain relevant. The article discusses the role of inflammatory mediators, in particular nitric oxide as a key factor in the generation of inflammatory response and brake the main neurotransmitter in the gut in the pathogenesis of the small intestine motor disorders during endotoxemia. Also discusses anti-inflammatory cholinergic path, which is realized with the participation of the autonomic nervous system. Possible mechanisms by which tributyrinte as a component of nutritional support creates a multiplier effect in arresting the inflammatory response and normalization of intestinal motility are suggested.

Time course of neural and contractile disturbances in a rat model of colitis induced by Trichinella spiralis

Colitis induced by Trichinella spiralis in rat induces alterations in the spontaneous motor pattern displayed by circular colonic muscle [Auli, M., Fernandez, E., 2005. Characterization of functional and morphological changes in a rat model of colitis induced by T. spiralis. Digestive Diseases and Sciences 50(8), 1432-1443]. We examined the temporal relationship between the severity of inflammation and the altered contractility of the underlying circular muscle as well as the role of NANC inhibitory pathways in the disruption of the motility pattern. Colitis was induced by intrarectal administration of T. spiralis larvae. Responses to acetylcholine (ACh) and increased extracellular potassium as well as the effect of tetrodotoxin (TTX, 1 microM), N-nitro-l-arginine (L-NOARG, 1 mM) and apamin (1 microM) were determined in vitro in the organ bath with circular muscle strips from sham-infected and infected rats at days 2-30 postinfection (PI). Microelectrode recordings were performed to study the putative changes in electrical activity of colonic smooth muscle cells. Responses to ACh and KCl were decreased at all days PI compared to sham. Intracellular calcium depletion had a greater inhibitory effect in inflamed tissue (6-14 PI). The effect of TTX, L-NOARG and apamin on the spontaneous contractions was found to be altered in all infected rats, i.e. their effects were transient and milder. Inflamed tissue showed lower resting membrane potential and a decreased duration of inhibitory junction potentials induced by electrical stimulation. These data suggest that the decreased contractility of colonic circular smooth muscle induced by the intrarectal T. spiralis infection results from the impairment of the excitation-contraction coupling, from a persistent hyperpolarization of smooth muscle cells and from impaired NANC inhibitory neurotransmission.

Relationships between the autonomic nervous system, humoral factors and immune functions in the intestine

The mammalian intestinal epithelium is a unique model for studying cellular differentiation since it undergoes continuous and rapid renewal. Substantial new information has accumulated on the mechanisms of regulation of the gene expression (e.g. Wnt, Hedgehog, bone morphogenic proteins), and the cell proliferation and apoptosis of the intestine. New knowledge has been gained in areas of genetics, central nervous system and enteric nervous system neurotransmitters (e.g. serotonin, corticotrophin-releasing factor, endogenous cannabinoid system, pathogen associated molecular patterns) of motility, sensitivity and secretion, the effect of altered mucosal inflammation on cytokine and paracrine activation, and neural sensitization, postinfectious disorders, the influence of psychologic stress on gut functioning through alterations in regulatory pathways, and improved accuracy of diagnosis both at the gut and brain level. In addition, acknowledgement of these mechanisms might help to develop strategies for therapy of neuronal abnormalities, which cause different gastrointestinal disease (e.g. irritable bowel syndrome, Crohn's disease). The present review focuses on the relationships between the gene expression and the intestine, and furthermore, presents the evidence and gastrointestinal diseases of the autonomic nervous system, the humoral factors, and the immune functions related intestinal proliferation and apoptosis.

The influence of rejection on graft motility after intestinal transplantation in swine: the possibility of using this method for the real-time monitoring of acute cellular rejection

BACKGROUND

We have previously reported that rejected allografts show dysmotility, which can be detected by real-time monitoring in swine. We examined the correlation between the motility and the mucosal histology to detect rejection at an early stage by real-time monitoring.

METHODS

Intestinal transplantation was performed orthotopically using FK506. The distal segment of the allograft measuring about 20 cm was isolated and exteriorized as "Thiry-Vella" stoma for biopsies. Strain-gage force transducers were attached on a graft for the real-time monitoring of graft motility. The pigs without intestinal transplantation were used as controls (C). The rejection was classified into 4 groups based on the histologic findings: nonrejection, mild rejection, moderate rejection, and severe rejection. Migrating motor complex (MMC) phase 3 was estimated by the following parameters: duration, amplitude, interval, motility index, velocity, and frequency of the propagation.

RESULTS

In the nonrejection group, all parameters were almost the same as in C group. In contrast, in the moderate rejection and severe rejection groups, most of the parameters were significantly lower than those in the C group. In the mild rejection group, the contractility of the MMC was not significantly altered, but the frequency of the propagation decreased significantly.

CONCLUSIONS

The graft motility detected by the real-time strain-gage method correlated closely to the grade of mucosal histology. This method is therefore considered to be useful for detecting rejection at an early stage by examining the frequency of MMC propagation.

Inhibition of macrophage function prevents intestinal inflammation and postoperative ileus in rodents

BACKGROUND

Abdominal surgery results in a molecular and cellular inflammatory response in the intestine, leading to postoperative ileus. It was hypothesised that resident macrophages within the intestinal muscularis have an important role in this local inflammation.

AIMS

To investigate whether chemical or genetic depletion of resident muscularis macrophages would lead to a reduction in the local inflammation and smooth-muscle dysfunction.

METHODS

Two rodent models were used to deplete and inactivate macrophages: (1) a rat model in which resident macrophages were depleted by chlodronate liposomes; (2) a model of mice with osteopetrosis mice, completely lacking the resident muscularis macrophages, used as an additional genetic approach. Animals with normal or altered intestinal macrophages underwent surgical intestinal manipulation. The inflammatory response was investigated by quantitative reverse transcriptase-polymerase chain reaction for mRNA of MIP-1alpha, interleukin (IL)1beta, IL6, intracellular adhesion molecule 1 (ICAM-1) and monocyte chemotractant protein 1 (MCP)-1 in the isolated small bowel muscularis. In addition, muscularis whole mounts were used for histochemical and immunohistochemical analysis to quantify leucocyte infiltration and detect cytokine expression. Subsequently, in vitro muscle contractility and in vivo gastrointestinal transit were measured.

RESULTS

Both models resulted in markedly decreased expression of MIP-1alpha, IL1beta, IL6, ICAM-1 and MCP-1 after manipulation compared with controls. In addition to this decrease in inflammatory mediators, recruitment of leucocytes into the muscularis was also diminished. Macrophage-altered animals had near normal in vitro jejunal circular muscle function and gastrointestinal transit despite surgical manipulation.

CONCLUSIONS

Resident intestinal muscularis macrophages are initially involved in inflammatory responses resulting in postoperative ileus. Depletion and inactivation of the muscularis macrophage network prevents postoperative ileus.

Adaptive immunity-dependent intestinal hypermotility contributes to host defense against Giardia spp

Humans infected with Giardia exhibit intestinal hypermotility, but the underlying mechanisms and functional significance are uncertain. Here we show in murine models of giardiasis that small-intestinal hypermotility occurs in a delayed fashion relative to peak parasite burden, is dependent on adaptive immune defenses, and contributes to giardial clearance.

Biliverdin protects against polymicrobial sepsis by modulating inflammatory mediators

Highly inducible heme oxygenase (HO)-1 is protective against acute and chronic inflammation. HO-1 generates carbon monoxide (CO), ferrous iron, and biliverdin. The aim of this study was to investigate the protective effects of biliverdin against sepsis-induced inflammation and intestinal dysmotility. Cecal ligation and puncture (CLP) was performed on Sprague-Dawley rats under isoflurane anesthesia with and without intraperitoneal biliverdin injections, which were done before, at the time of CLP, and after CLP. In vivo gastrointestinal transit was carried out with fluorescein-labeled dextran. Jejunal circular muscle contractility was quantified in vitro using organ bath-generated bethanechol dose-response curves. Neutrophilic infiltration into the muscularis externa was quantified. The jejunal muscularis was studied for cytokine mRNA expressions [interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1, inducible nitric oxide synthase, cyclooxygenase-2, biliverdin, IL-10, and HO-1] using real-time RT-PCR. Biliverdin treatment prevented the sepsis-induced suppression of gastrointestinal muscle contractility in vivo and in vitro and significantly decreased neutrophilic infiltration into the jejunal muscularis. Inflammatory mRNA expressions for small bowel IL-6 and MCP-1 were significantly reduced after biliverdin treatment in CLP-induced septic animals compared with untreated septic animals. The anti-inflammatory mediator expression of small bowel IL-10 was significantly augmented after CLP at 3 h compared with untreated septic animals. These findings demonstrate that biliverdin attenuates sepsis-induced morbidity to the intestine by selectively modulating the inflammatory cascade and its subsequent sequelae on intestinal muscularis function.

Gut motor function: immunological control in enteric infection and inflammation

Alteration in gastrointestinal (GI) motility occurs in a variety of clinical settings which include acute enteritis, inflammatory bowel disease, intestinal pseudo-obstruction and irritable bowel syndrome (IBS). Most disorders affecting the GI tract arise as a result of noxious stimulation from the lumen via either microbes or chemicals. However, it is not clear how injurious processes initiated in the mucosa alter function in the deeper motor apparatus of the gut wall. Activation of immune cells may lead to changes in motor-sensory function in the gut resulting in the development of an efficient defence force which assists in the eviction of the noxious agent from the intestinal lumen. This review addresses the interface between immune and motor system in the context of host resistance based on the studies in murine model of enteric nematode parasite infection. These studies clearly demonstrate that the infection-induced T helper 2 type immune response is critical in producing the alterations of infection-induced intestinal muscle function in this infection and that this immune-mediated alteration in muscle function is associated with host defence mechanisms. In addition, by manipulating the host immune response, it is possible to modulate the accompanying muscle function, and this may have clinical relevance. These observations not only provide valuable information on the immunological control of gut motor function and its role in host defence in enteric infection, but also provide a basis for understanding pathophysiology of gastrointestinal motility disorders such as in IBS.

Functional importance of regional differences in localized gene expression of receptors for IL-13 in murine gut

IL-13 induces a STAT6-dependent hypercontractility of intestinal smooth muscle that is mediated by binding to the IL-13Ralpha1 component of the type 2 IL-4R that is linked to STAT6. IL-13 also binds to the IL-13Ralpha2 that is not linked to STAT6 and functions to limit the effects of IL-13 in vivo. In this study we assessed the contributions of regional and cellular differences in the distribution of the IL-13R components to the physiological regulation of smooth muscle function in wild-type mice and mice deficient in STAT6 or IL-13Ralpha2. The expression of IL-13 and IL-13Ralpha2 was higher in colon than in small intestine. Laser capture microdissection of specific cell types revealed that the expression of IL-13Ralpha2 was higher in the smooth muscle layer compared with levels in the epithelial cells of the mucosa. In contrast, there was a uniform distribution of IL-13alpha1 in smooth muscle, epithelia, and myenteric neurons. The significant hypercontractility of smooth muscle in mice deficient in IL-13Ralpha2, but not in STAT6, shows the physiological importance of IL-13 binding to IL-13Ralpha2. The pronounced differences in the expression of IL-13Ralpha2 suggest that the gut has developed sophisticated mechanisms for controlling the physiological and pathophysiological activities of IL-13.

Neuronal nitric oxide synthase is necessary for elimination of Giardia lamblia infections in mice

NO produced by inducible NO synthase (NOS2) is important for the control of numerous infections. In vitro, NO inhibits replication and differentiation of the intestinal protozoan parasite Giardia lamblia. However, the role of NO against this parasite has not been tested in vivo. IL-6-deficient mice fail to control Giardia infections, and these mice have reduced levels of NOS2 mRNA in the small intestine after infection compared with wild-type mice. However, NOS2 gene-targeted mice and wild-type mice treated with the NOS2 inhibitor N-iminoethyl-L-lysine eliminated parasites as well as control mice. In contrast, neuronal NOS (NOS1)-deficient mice and wild-type mice treated with the nonspecific NOS inhibitor NG-nitro-L-arginine methyl ester and the NOS1-specific inhibitor 7-nitroindazole all had delayed parasite clearance. Finally, Giardia infection increased gastrointestinal motility in wild-type mice, but not in SCID mice. Furthermore, treatment of wild-type mice with NG-nitro-L-arginine methyl ester or loperamide prevented both the increased motility and the elimination of parasites. Together, these data show that NOS1, but not NOS2, is necessary for clearance of Giardia infection. They also suggest that increased gastrointestinal motility contributes to elimination of the parasite and may also contribute to parasite-induced diarrhea. Importantly, this is the first example of NOS1 being involved in the elimination of an infection.

Lactobacillus paracasei normalizes muscle hypercontractility in a murine model of postinfective gut dysfunction

BACKGROUND & AIMS

The effects of probiotics on gut dysfunction in postinfective irritable bowel syndrome are unknown. We tested whether probiotics influence persistent muscle hypercontractility in mice after recovery from infection with Trichinella spiralis and analyzed the underlying mechanisms.

METHODS

Mice were gavaged with Lactobacillus paracasei, Lactobacillus johnsonii, Bifidobacterium longum, or Bifidobacterium lactis in spent culture medium from days 10 to 21 after infection. Additional mice received heat-inactivated Lactobacillus paracasei, Lactobacillus paracasei -free spent culture medium, or heat-inactivated Lactobacillus paracasei -free spent culture medium. Lactobacilli enumeration, immunohistochemistry, and cytokine detection (enzyme-linked immunosorbent assay) were performed. Mice were also treated with Lactobacillus paracasei or Lactobacillus paracasei -free spent culture medium from days 18 to 28 after infection. Contractility was measured on days 21 and 28 after infection.

RESULTS

Lactobacillus paracasei, but not Lactobacillus johnsonii, Bifidobacterium lactis, or Bifidobacterium longum, attenuated muscle hypercontractility. This was associated with a reduction in the Trichinella spiralis -associated T-helper 2 response and a reduction in transforming growth factor-beta1, cyclooxygenase-2, and prostaglandin E 2 levels in muscle. Attenuation of muscle hypercontractility by Lactobacillus paracasei -free spent culture medium was abolished after heat treatment. Improvement of muscle hypercontractility at day 28 after infection was also observed after the administration of Lactobacillus paracasei or Lactobacillus paracasei -free spent culture medium from day 18 after infection.

CONCLUSIONS

Probiotics show strain-dependent attenuation of muscle hypercontractility in an animal model of postinfective irritable bowel syndrome. This likely occurs via both a modulation of the immunologic response to infection and a direct effect of Lactobacillus paracasei or a heat-labile metabolite on postinfective muscle hypercontractility. Lactobacillus paracasei may be useful in the treatment of postinfective irritable bowel syndrome.

Visceral hyperalgesia and intestinal dysmotility in a mouse model of postinfective gut dysfunction

BACKGROUND & AIMS

We established the concept that transient enteric infection may lead to persistent gut dysfunction, evident in vitro, in nematode-infected mice. The present study determined whether gut dysfunction in this model involves motor and sensory changes reminiscent of changes found in patients with postinfective irritable bowel syndrome (PI-IBS) and investigated underlying mechanisms.

METHODS

Mice infected up to 70 days previously with Trichinella spiralis (Tsp) underwent videofluoroscopy with image analysis to assess upper gastrointestinal motility. Pseudoaffective responses to colorectal distention (CRD) were assessed using a barostat and validated by single fiber recordings from spinal nerves during CRD. Tissues were examined at different time points for histology, immunohistochemistry, and cytokine analysis. Some mice received dexamethasone intraperitoneally on days 23-25 PI or Tsp antigen orally on days 29, 43, and 57 PI.

RESULTS

From day 28 PI, no discernible inflammation was present in the gut. Frequency and propagation velocity of intestinal contractions decreased, and retroperistalsis increased at days 28 to 42 PI. CRD induced an allodynic and hyperalgesic response in PI mice, which was accompanied by increased single unit discharge. Gavage of Tsp antigen induced T-cell responses and sustained gut dysfunction for 70 days PI. Administration of dexamethasone postinfection normalized dysmotility and visceral hyperalgesia.

CONCLUSIONS

Long-lasting gut dysmotility and hyperalgesia develop in mice after transient intestinal inflammation. These changes are maintained by luminal exposure to antigen and reversed by corticosteroid treatment. The findings prompt consideration of this as a model of PI-IBS.

Pathophysiology, diagnosis and treatment of food protein-induced gastrointestinal diseases

PURPOSE OF REVIEW

Although our general understanding of food hypersensitivity has improved in recent years, gastrointestinal food protein-induced diseases still pose diagnostic and therapeutic dilemmas.

RECENT FINDINGS

Food allergy in children and adults may involve any part of the gastrointestinal tract. Clinical presentations include protein-induced enterocolitis syndrome, enteropathy and proctocolitis, as well as eosinophilic gastroenteritis and related disorders. For many of these conditions, our understanding of the pathophysiology is incomplete. Manifestations are mostly non-IgE mediated, and skin prick testing and measurement of food-specific IgE antibody levels are of limited diagnostic value. Atopy patch testing may be of benefit in identifying food items associated with late-onset gastrointestinal reactions. A definitive diagnosis of gastrointestinal food allergy, however, still relies on formal food challenges. Depending on the clinical presentation, gastrointestinal biopsies may be required. In infancy, hypoallergenic formula or maternal elimination diets have been shown to effectively control the gastrointestinal manifestations of food allergies. Growth parameters and micronutrient levels need to be carefully monitored while on elimination diets for prolonged periods. In older children and adults with eosinophilic gastrointestinal disorders, the response to dietary restriction is variable. Corticosteroids may be required to control symptoms in those who failed to respond to hypoallergenic diets. In eosinophilic esophagitis, steroids can be administered topically in the form of swallowed aerosols. Leukotriene receptor antagonists and other novel therapies may be useful as steroid-sparing agents.

SUMMARY

Early diagnosis and treatment of food protein-induced gastrointestinal diseases may prevent significant nutritional complications. Further research is needed to develop diagnostic tools for these mainly cell-mediated disorders.

Postoperative ileus is maintained by intestinal immune infiltrates that activate inhibitory neural pathways in mice

BACKGROUND AND AIMS

Postoperative ileus after abdominal surgery largely contributes to patient morbidity and prolongs hospitalization. We aimed to study its pathophysiology in a murine model by determining gastric emptying after manipulation of the small intestine.

METHODS

Gastric emptying was determined at 6, 12, 24, and 48 hours after abdominal surgery by using scintigraphic imaging. Intestinal or gastric inflammation was assessed by immune-histochemical staining and measurement of tissue myeloperoxidase activity. Neuromuscular function of gastric and intestinal muscle strips was determined in organ baths.

RESULTS

Intestinal manipulation resulted in delayed gastric emptying up to 48 hours after surgery; gastric half-emptying time 24 hours after surgery increased from 16.0 +/- 4.4 minutes after control laparotomy to 35.6 +/- 5.4 minutes after intestinal manipulation. The sustained delay in gastric emptying was associated with the appearance of leukocyte infiltrates in the muscularis of the manipulated intestine, but not in untouched stomach or colon. The delay in postoperative gastric emptying was prevented by inhibition of intestinal leukocyte recruitment. In addition, postoperative neural blockade with hexamethonium (1 mg/kg intraperitoneally) or guanethidine (50 mg/kg intraperitoneally) normalized gastric emptying without affecting small-intestinal transit. The appearance of intestinal infiltrates after intestinal manipulation was associated with increased c-fos protein expression in sensory neurons in the lumbar spinal cord.

CONCLUSIONS

Sustained postoperative gastroparesis after intestinal manipulation is mediated by an inhibitory enterogastric neural pathway that is triggered by inflammatory infiltrates recruited to the intestinal muscularis. These findings show new targets to shorten the duration of postoperative ileus pharmacologically.

Immunomodulatory effects of inhaled carbon monoxide on rat syngeneic small bowel graft motility

BACKGROUND

Intestinal transplantation provokes an intense inflammatory response within the graft muscularis that causes intestinal ileus. We hypothesised that endogenously produced anti-inflammatory substances could be utilised as novel therapeutics. Therefore, we tested the protective effects of inhaled carbon monoxide (CO) and an endogenous haeme oxygenase 1 (HO-1) anti-inflammatory mediator on transplant induced inflammatory responses and intestinal ileus in the rat.

METHODS

Gastrointestinal transit of non-absorbable FITC labelled dextran and in vitro jejunal circular muscle contractions were measured in controls and syngeneic orthotopic transplanted animals with and without CO inhalation (250 ppm for 25 hours). Inflammatory mRNAs for interleukin (IL)-6, IL-1beta, tumour necrosis factor alpha (TNF-alpha), intercellular adhesion molecule 1 (ICAM-1), inducible nitric oxide (iNOS), cyclooxygenase 2 (COX-2), and IL-10 were quantified by real time reverse transcriptase-polymerase chain reaction and HO-1 by northern blot. Histochemical stains characterised neutrophil infiltration and enterocyte apoptosis.

RESULTS

Transplantation delayed transit and suppressed jejunal circular muscle contractility. Transplantation induced dysmotility was significantly improved by CO inhalation. Transplantation initiated a significant upregulation in IL-6, IL-1beta, TNF-alpha, ICAM-1, iNOS, COX-2, and HO-1 mRNAs with the graft muscularis. CO inhalation significantly decreased expression of IL-6, IL-1beta, iNOS, and COX-2 mRNAs. CO also significantly decreased serum nitrite levels (iNOS activity).

CONCLUSIONS

CO inhalation significantly improved post-transplant motility and attenuated the inflammatory cytokine milieu in the syngeneic rat transplant model. Thus clinically providing CO, the end product of the anti-inflammatory HO-1 pathway, may prove to be an effective therapeutic adjunct for clinical small bowel transplantation.

Study of the pathogenesis of paralytic ileus in animal models of experimentally induced postoperative and septic ileus

Paralytic ileus is defined as an inhibition of propulsive intestinal motility. Postoperative ileus is the most common type, however, also during sepsis and critical illness paralytic ileus is a common finding. The pathogenesis of paralytic ileus is still debated. It is believed to result from the activation of inhibitory neural reflex pathways and activation of inflammatory processes. It is generally accepted that postoperative ileus results from the activation of an inhibitory neural reflex pathway. In our rat model we showed that different degrees of nociceptive stimulation activate different reflex pathways: laparatomy activates an adrenergic inhibitory reflex pathway, whereas manipulation results in additional activation of inhibitory NANC neurons releasing NO and VIP as neurotransmitters. We also demonstrated that blockade of the afferent limb of the reflex pathway by peripheral kappa-opioid agonists or by non-steroidal anti-inflammatory drugs ameliorated postoperative ileus. However, the use of prokinetics lead to disappointing results. In the murine septic model we demonstrated an important role for activation of inducible NO synthase in the endotoxin-induced delay in gastric emptying and small intestinal transit. We hypothesise that activation of the residential macrophages in the gut wall leads to the production of iNOS and other inflammatory mediators. These mediators will attract more inflammatory cells and influence smooth muscle contractility. Next, we provide evidence that production of iNOS results in the activation of guanylyl cyclase leading to the production of cGMP and smooth muscle relaxation. However, a parallel mechanism of action for NO via oxidative stress needs further investigation.

Antibody-mediated gastrointestinal dysmotility in scleroderma

BACKGROUND & AIMS

Defects in enteric excitatory neurotransmission have been proposed to underlie the gastrointestinal dysmotility associated with scleroderma (systemic sclerosis). This study investigated whether patients with scleroderma produce antibodies that inhibit M3-muscarinic or neurokinin receptor-mediated intestinal contractions, either directly or via an effect on L-type voltage-gated calcium channels (VGCCs).

METHODS

Responses of mouse colon longitudinal muscle to stimulation by the muscarinic agonist carbachol (1-300 micromol/L) and neurokinin-1 and -2 receptor agonists were measured in the absence and presence of serum (2%) or immunoglobulin G (IgG) (0.3-1.0 mg/mL) from patients with scleroderma, those with other autoimmune disorders, and healthy controls. The role of L-type VGCCs in carbachol- and tachykinin-evoked contractions was assessed using nicardipine.

RESULTS

M3-muscarinic receptor-mediated contractions were inhibited by Ig fractions from 7 of 9 patients with scleroderma (limited and diffuse forms), 4 of 4 patients with primary Sjögren's syndrome, and 3 of 3 patients with secondary Sjögren's syndrome. Ig fractions from healthy controls did not inhibit the M3-muscarinic receptor-mediated contractions. Inhibition by Ig was concentration-dependent; a maximum inhibition of approximately 40% occurred at 0.6 mg/mL IgG. Both M3-muscarinic and neurokinin receptor-mediated contractions were L-type VGCC dependent. Patient sera had no effect on responses to neurokinin receptor stimulation, demonstrating the lack of antibodies inhibiting L-type VGCCs.

CONCLUSIONS

Functional antibodies specifically inhibiting M3-muscarinic receptor-mediated enteric cholinergic neurotransmission may provide a pathogenic mechanism for the gastrointestinal dysfunction seen in patients with scleroderma.

Colonic postoperative inflammatory ileus in the rat

OBJECTIVE

To investigate local inflammatory events within the colonic muscularis as a causative factor of postoperative ileus.

SUMMARY BACKGROUND DATA

Surgically induced intestinal muscularis inflammation has been hypothesized as a mechanism for postoperative ileus. The colon is a crucial component for recovery of gastrointestinal motor function after surgery but remains unaddressed. The authors hypothesize that colonic manipulation initiates inflammatory events that directly mediate postoperative smooth muscle dysfunction.

METHODS

Rats underwent colonic manipulation. In vivo transit and colonic motility was estimated using geometric center analysis and intraluminal pressure monitoring. Leukocyte extravasation was investigated in muscularis whole mounts. Mediator mRNA expression was determined by real-time reverse transcriptase-polymerase chain reaction. In vitro circular muscle contractility was assessed in a standard organ bath. The relevance of iNOS and COX-2 inhibition was determined using DFU or L-NIL perfusion.

RESULTS

Colonic manipulation resulted in a massive leukocyte recruitment and an increase in inflammatory mRNA expression. This inflammatory response was associated with an impairment of in vivo motor function and an inhibition of in vitro smooth muscle contractility (56%). L-NIL but not DFU significantly ameliorated smooth muscle dysfunction.

CONCLUSIONS

The results provide evidence for a surgically initiated local inflammatory cascade within the colonic muscularis that mediates smooth muscle dysfunction, which contributes to postoperative ileus.

Role of IL-4, IL-13, and STAT6 in inflammation-induced hypercontractility of murine smooth muscle cells

T helper 2 (Th2) cytokines interleukin (IL)-4 and IL-13, which activate signal transducer and activator of transcription 6 (STAT6) are expressed in the muscularis externa during nematode infection and are candidate mediators of the associated hypercontractility. To determine the locus of action of these cytokines, we examined the IL-4- and IL-13-induced hypercontractility of the isolated muscle cells from STAT6 +/+ and STAT6 -/- mice. We compared the results with cells isolated from Trichinella spiralis-infected STAT6 +/+ and STAT6 -/- mice. Carbamylcholine chloride (Carbachol) induced the contraction of jejunal muscle cells in a concentration-dependent manner maximal contraction (R(max) 26.7 +/- 1.9%). Cells from T. spiralis-infected STAT6 -/- mice showed the hypertrophy (cell lengths 41.4 +/- 0.8 to 89.0 +/- 8.7 microm) and hypercontractility (R(max) 37.5 +/- 1.3%) induced by infection. IL-4Ralpha mRNA was detected in dispersed smooth muscle cells. Incubation of longitudinal muscle-myenteric plexus (LMMP) with IL-4 and IL-13 enhanced Carbachol-induced muscle contraction (R(max) 35.5 +/- 1.9 and 32.4 +/- 2.9%, respectively). Incubation of LMMP from STAT6 -/- mice with IL-4 did not enhance the contraction. The hypercontractility in T. spiralis-infected mice was attenuated in STAT6 -/- mice (P < 0.02). These results indicate both IL-4 and IL-13 induce hypercontractility of muscle cells via the STAT6 pathway, and this is the basis for hypercontractility observed in T. spiralis-infected mice.

A role for autoantibodies in some cases of acquired non-paraneoplastic gut dysmotility

BACKGROUND

Antibody-mediated autoimmunity underlies a diverse range of disorders, particularly in the nervous system where domains of ion channels and receptors are potential targets. The aetiology of many adult-onset conditions of severe gut dysmotility is not known. We looked for antibodies to neuronal antigens in patients with severe (slow-transit-type) constipation (STC).

METHODS

Eleven sera from adult-onset STC patients and 18 from childhood onset cases were tested by routine immunoprecipitation assays for antibodies against neuronal antigens including voltage-gated potassium channels (VGKCs), calcium channels (VGCCs), both muscle and neuronal acetylcholine receptor and glutamic acid decarboxylase (GAD). Results were compared with positive and negative control populations.

RESULTS

Two of the 11 sera from patients with adult-onset STC showed highly positive anti-VGKC antibodies. Both had onset of symptoms de novo in adulthood without evidence of autoimmune, neoplastic or neurological disease. One of these patients, and one other, had anti-GAD antibodies. None of the childhood-onset STC had evidence of anti-neuronal antibodies.

CONCLUSIONS

Anti-neuronal antibodies are found in some patients with a condition of severe acquired gut dysmotility of previously unknown aetiology. Future studies may demonstrate an autoimmune role for such antibodies.

MCP-1 causes leukocyte recruitment and subsequently endotoxemic ileus in rat

Endotoxemia causes an inflammatory response within the intestinal muscularis and gastrointestinal dysmotility. We hypothesize that the resident macrophage-derived chemokine monocyte chemoattractant protein-1 (MCP-1) plays a significant role in the recruitment of leukocytes into the lipopolysaccharide (LPS)-stimulated rat intestinal muscularis. MCP-1 mRNA expression was investigated by RT-PCR. Leukocyte extravasation and MCP-1 protein localization were determined by immunohistochemistry. Contractile activity was assessed by using a standard organ bath in rats that were treated with saline, recombinant MCP-1, LPS, LPS + nonspecific antibody, or LPS + MCP-1 antibody. Endotoxemia caused a significant 280-fold increase in MCP-1 mRNA expression in the muscularis, peaking at 3 h. MCP-1 protein was immunohistochemically located to muscularis macrophages. LPS application caused significant leukocyte recruitment into the muscularis and a 51% decrease in muscle contractility. MCP-1 antibody treatment significantly averted leukocyte recruitment and significantly prevented muscle dysfunction. These parameters were not significantly altered by the nonspecific antibody. Results show that resident muscularis macrophage-derived MCP-1 plays a major role in the recruitment of monocytes during endotoxemia, which then subsequently secrete kinetically active substances that cause ileus.

Gastric IgA in cystic fibrosis in relation to the migrating motor complex

BACKGROUND

Gastrointestinal symptoms in cystic fibrosis are frequent, but little is known about the underlying pathophysiology. Mucosal secretion of IgA is important for the immunologic function in the human gastrointestinal tract but has not been studied in cystic fibrosis. The aim of this study was to quantify the release of IgA by the gastric mucosa in relation to interdigestive motor activity in patients with cystic fibrosis with different genotypes.

METHODS

The study included 7 healthy adult volunteers and 10 adult patients with cystic fibrosis, all Helicobacter pylori-negative. All patients had pathological sweat tests and clinical symptoms and signs of cystic fibrosis. All but one were colonized with Pseudomonas aeruginosa. Three patients were pancreatic sufficient. The investigation was performed using intragastric perfusion and gastroduodenal manometry.

RESULTS

During the investigation, 8 of 10 patients with cystic fibrosis showed the characteristic pattern of interdigestive motility. The patients had significantly lower levels of gastric IgA compared to healthy subjects during phases II and III of migrating motor complex, median (range) 120 (67-442) and 36 (6-299) microg/5 min. 382 (40-1176) and 56 (4-398) (P = 0.03 and P = 0.04), respectively. Only one patient with genotype R668C/unknown showed IgA levels within the normal range. There was no correlation to gastric presence of duodenogastric reflux markers.

CONCLUSION

The interdigestive motility pattern was normal in most patients with cystic fibrosis. The low levels of IgA released from the gastric mucosa in the patients might indicate a defective gastric transmucosal IgA transport in cystic fibrosis.

Impaired gut contractility following hemorrhagic shock is accompaied by IL-6 and G-CSF production and neutrophil infiltration

Recovery from hemorrhagic shock (HS) is frequently accompanied by bowel stasis. The aim of this study was to examine whether or not HS initiates an inflammatory response that includes production of cytokines, specifically G-CSF and interleukin-6 (IL-6), and recruitment of leukocytes within the intestinal muscularis which contribute to impaired muscle contractility. Sprague-Dawley rats were subjected to HS (MAP 40 mm Hg for 156 min) followed by resuscitation, and then they were killed at 4 hr. Shock animals demonstrated accumulation of PMNs in the jejunal muscularis and decreased spontaneous and bethanechol-stimulated muscle contractility. Semiquantitative RT-PCR demonstrated elevated levels of IL-6 and G-CSF mRNA in shock animals in full-thickness jejunum and in mucosa and muscularis layers compared to sham controls. Immunostaining demonstrated increased IL-6 protein production within the muscularis externa and submucosa. In situ hybridization studies localized G-CSF mRNA production to the submucosa. Gel shift assays revealed increased NF-kappaB and Stat3 activity in full-thickness jejunum and jejunal layers of shock animals. Activation of Stat3 also was demonstrated in normal muscularis tissue exposed to IL-6 and G-CSF in vitro. IL-6 and G-CSF are produced in the muscularis and mucosa layers of the gut in HS where they may contribute to PMN recruitment and smooth muscle dysfunction.

Effect of splanchnectomy on jejunal motility and fos expression in brain stem after intestinal anaphylaxis in rat

This study was to determine whether alterations in jejunal motility observed after antigen challenge of sensitized rats occurred after extirpation of the celiac-superior mesenteric ganglia. Hooded-Lister rats were prepared with an intact or extirpated celiac-superior mesenteric ganglion, an isolated Thiry-Vella loop of ileum for instillation of antigen, and jejunal electrodes for myoelectric recording. Animals were sensitized by injection of 10 microg egg albumin (EA, ip), and specific anti-EA IgE titers were determined to be >1:64. In both control and splanchnectomized rats, normal fasting migrating myoelectric complexes (MMC) were observed before challenge with EA. MMCs were disrupted, and diarrhea was observed immediately after EA challenge of control but not splanchnectomized animals. Brain stems were removed and processed for Fos immunoreactivity. The absence of perivascular neuropeptide Y immunoreactivity in the submucosa was used to confirm the success of splanchnectomy. The number of Fos-immunoreactive neuronal nuclei was significantly reduced in the brain stem after splanchnectomy. Thus the mesenteric sympathetic ganglia are an integral part of the extramural neuronal pathways required for altered motility in this model of intestinal anaphylaxis.

Myenteric neuronal antibodies in scleroderma: passive transfer evokes alterations in intestinal myoelectric activity in a rat model

Although the mechanism for neuropathic gastrointestinal motility disturbances in scleroderma is unknown, we have previously described anti-myenteric antibodies in some patients with scleroderma. The aim of this study was to screen patients with scleroderma who had gastrointestinal symptoms for the presence of anti-myenteric neuronal antibodies and then purify the immunoglobulin G (IgG) fraction from serum samples for passive immunization into a rat model and observe for intestinal motility effects. Patients with scleroderma were screened, a serum sample from a patient with high titer anti-myenteric neuronal antibodies was obtained, and IgG was purified. Using a rat model with chronic indwelling intestinal electrodes to measure intestinal myoelectric activity, we passively transferred the IgG from either control subjects or this patient with scleroderma. We immunosuppressed the rats and intraperitoneally injected IgG from control subjects and this patient with scleroderma daily for 7 days. Recordings of myoelectric activity in control injected rats revealed no difference from baseline, but a prolongation in the activity front duration and interval and a disruption were seen after scleroderma IgG injections. IgG from a patient with scleroderma with antimyenteric neuronal antibodies, when passively immunized into a rat model, evokes intestinal myoelectric activity alterations. We hypothesize that these antibodies could account for the gastrointestinal neuropathic motility disturbances seen in scleroderma.

Anaphylaxis-induced alterations in intestinal motility: role of extrinsic neural pathways

The roles of mast cells and extrinsic and vagal neural pathways in the anaphylaxis-induced alterations in motility observed at sites remote from antigen exposure were explored. Rats were sensitized to egg albumin (EA) and prepared with 1) electrodes to monitor intestinal myoelectric activity, 2) an isolated intestinal loop, and 3) either intact vagal innervation or a subdiaphragmatic vagotomy. Fasting myoelectric activity was recorded before and after challenge of the jejunum in continuity or the isolated loop with EA or BSA. Intestinal segments and the brain stems were processed for mast cell identification (intestine) or Fos immunoreactivity (brain stem). EA but not BSA challenge of the jejunum or the isolated loop induced altered motility at both sites and diarrhea. Granulated mast cells were significantly reduced at the site local to but not remote from challenge. Vagotomy did not inhibit antigen-induced alterations in motility or diarrhea. The number of Fos-immunoreactive nuclei in vagal sensory or motor nuclei was not significantly altered by vagotomy. Thus antigen challenge of sensitized animals causes mast cell degranulation only at the site of direct challenge but alters motility at sites local and remote from challenge. The remote response requires intact extrinsic but not necessarily vagal neural pathways.

Colonic and jejunal motor disturbances after colonic antigen challenge of sensitized rat

BACKGROUND & AIMS

Inflammation in the colon may alter motility in the proximal gut and potentiate clinical symptoms. The aim of this study was to characterize the effect of colonic anaphylaxis on local (colonic) and remote (small intestinal) motility and identify the mechanism and mediators involved.

METHODS

Rats were sensitized by intraperitoneal injection of 10 microg egg albumin and surgically prepared with electrodes in jejunum and colon and a colostomy tube. Colonic and jejunal myoelectric activity were recorded in fasted animals before and after colonic antigen challenge without and then after pretreatment with specific antagonists.

RESULTS

Colonic antigen challenge of sensitized rats was associated with significant (1) increase in colonic myoelectric spike activity, (2) disruption of fasting jejunal motility and initiation of aborally propagating spike complexes, and (3) increase in plasma rat mast cell protease II levels with a decrease in granulated mast cells in colon but not jejunum. The myoelectric disturbance in both colon and jejunum was inhibited significantly by pretreatment with atropine and hexamethonium, doxantrazole, cyclooxygenase, and lipoxygenase inhibitors. Methysergide inhibited only the jejunal disturbance.

CONCLUSIONS

Colonic antigen challenge of sensitized animals results in local mast cell activation and the release of mediators that modulate neural pathways to initiate both a local colonic and a remote jejunal myoelectric disturbance.

The immunomodulation of enteric neuromuscular function: implications for motility and inflammatory disorders

Gastrointestinal motility and sensory perception are altered in a variety of mucosal inflammatory conditions of the gut, ranging from peptic esophagitis to ulcerative colitis. Studies in animal models now clearly indicate a causal relationship between the presence of mucosal inflammation and altered sensory-motor function. In many instances, these changes occur in the absence of any discernible encroachment of the deeper neuromuscular layers by the inflammatory infiltrate, which remains largely within the lamina propria. Accordingly, attention has focused on local sources of mediators, and recent studies indicate that smooth muscle cells and enteroglia are sources of and targets for cytokines such as interleukin 1 beta and interleukin 6. In several instances, neuromuscular dysfunction persists after mucosal inflammation has subsided; this state may be maintained by locally produced mediators. Studies also show the ability of enteric muscle to modulate lymphocyte function via major histocompatibility complex II-restricted antigen presentation. Clinical observation and experimental data also suggest that nerves modulate intestinal inflammation via local release of proinflammatory neuropeptides (substance P) and via the activation of extensive circuits that may involve the brain. Taken together, these findings provide plausible explanations for a variety of clinical scenarios ranging from inflammatory bowel disease to pseudo-obstruction syndromes and subgroups of functional bowel disorders.