Role of interleukin 10 in murine postoperative ileus

New insights into muscularis macrophages in the gut: from their origin to therapeutic targeting

Muscularis macrophages, as the most abundant immune cells in the intestinal muscularis externa, exhibit tissue protective phenotype in the steady state. Owing to tremendous advances in technology, we now know the fact that muscularis macrophages are a heterogeneous population of cells which could be divided into different functional subsets depending on their anatomic niches. There is emerging evidence showing that these subsets, through molecular interactions with their neighbours, take part in a wide range of physiological and pathophysiological processes in the gut. In this review, we summarize recent progress (particularly over the past 4 years) on distribution, morphology, origin and functions of muscularis macrophages and, where possible, the characteristics of specific subsets in response to the microenvironment they occupy, with particular emphasis on their role in muscular inflammation. Furthermore, we also integrate their role in inflammation-related gastrointestinal disorders, such as post-operative ileus and diabetic gastroparesis, in order to propose future therapeutic strategies.

The ghrelin agonist, HM01 activates central vagal and enteric cholinergic neurons and reverses gastric inflammatory and ileus responses in rats

BACKGROUND

Electrical vagal stimulation alleviates abdominal surgery (AS)-induced intestinal inflammation. Ghrelin receptors (GHS-Rs) are expressed in the brain and peripheral tissues. We investigated the influence of HM01, an orally active ghrelin agonist crossing the blood-brain barrier, on AS-induced gastric inflammation and emptying (GE) in rats.

METHODS

HM01 (6 mg/kg) or saline pretreatment was administered per orally (po) or intraperitoneally (ip). We assessed GE, gastric cytokine mRNA, and Fos positive cells in the dorsal motor nucleus of the vagus (DMN) and gastric corpus myenteric plexus (MP) in sham (anesthesia alone) and AS groups. The transcripts of GHS-R1 variants were determined in the medulla oblongata and gastric corpus of naïve rats.

KEY RESULTS

In vehicle pretreated rats, HM01 (ip) significantly increased the number of Fos immunoreactive cells in the MP and DMN in 55% and 52% of cholinergic neurons respectively. Hexamethonium did not modify HM01-induced Fos expression in the DMN while reducing it in the MP by 2-fold with values still significantly higher than that in control groups. AS upregulated gastric IL-1β and TNFα expression and inhibited GE by 66.6%. HM01 (po) abolished AS-induced gastric ileus and increased cytokine expression and elevated IL-10 by 4.0-fold versus vehicle/sham. GHS-R1a mRNA level was 5.4-fold higher than the truncated GHS-R1b isoform in the brain medulla and 40-fold higher in the gastric submucosa/muscle layers than in the mucosa.

CONCLUSIONS AND INFERENCE

Peripheral HM0 activates central vagal and myenteric cholinergic pathways that may influence both central and peripheral targets to prevent AS-induced gastric inflammatory and ileus.

A Novel "Inside-Out" Intraocular Nanomedicine Delivery Mode for Nanomaterials' Biological Effect Enhanced Choroidal Neovascularization Occlusion and Microenvironment Regulation

Photodynamic therapy (PDT) is commonly used in choroidal neovascularization (CNV) treatment due to the superior light transmittance of the eye. However, PDT often leads to surrounding tissue damage and further microenvironmental deterioration, including exacerbated hypoxia, inflammation, and secondary neovascularization. In this work, Pt nanoparticles (NPs) and Au NPs decorated zeolitic imidazolate framework-8 nanoplatform is developed to load indocyanine green for precise PDT and microenvironment amelioration, which can penetrate the internal limiting membrane through Müller cells endocytosis and target to CNV by surface-grafted cyclo(Arg-Gly-Asp-d-Phe-Lys) after intravitreal injection. The excessive H₂ O₂ in the CNV microenvironment is catalyzed by catalase-like Pt NPs for hypoxia relief and enhanced PDT occlusion of neovascular. Meanwhile, Au NPs show significant anti-inflammatory and anti-angiogenesis properties in regulating macrophages and blocking vascular endothelial growth factor (VEGF). Compared with verteporfin treatment, the mRNA expressions of hypoxia-inducible factor-1α and VEGF in the nanoplatform group are downregulated by 90.2% and 81.7%, respectively. Therefore, the nanoplatform realizes a comprehensive CNV treatment effect based on the high drug loading capacity and biosafety. The CNV treatment mode developed in this work provides a valuable reference for treating other diseases with similar physiological barriers that limit drug delivery and similar microenvironment.

Molecular and cellular mechanisms underlying postoperative paralytic ileus by various immune cell types

Postoperative ileus (POI) is a well-known complication following gut manipulation or surgical trauma, leading to an impaired gut motility and prolonged postoperative recovery time. Few current therapeutic strategies can prevent POI, and this disorder remains to be a major clinical challenge for patients undergoing surgery. Comprehensive understanding of cellular and molecular mechanisms related to the pathogenesis of POI stimulates the discovery of more promising targets for treatment. POI is closely associated with a series of inflammatory events within the bowel wall, and as key components of inflammatory mechanisms, different types of immune cells, including macrophages, dendritic cells, and T lymphocytes, play significant roles during the development of POI. A variety of immune cells are recruited into the manipulation sites after surgery, contributing to early inflammatory events or impaired gut motility. Our review intends to summarize the specific relationship between different immune cells and POI, mainly focusing on the relevant mechanisms underlying this disorder.

Postoperative Ileus: a Pharmacological Perspective

Post-operative ileus (POI) is a frequent complication after abdominal surgery. The consequences of POI can be potentially serious such as bronchial inhalation or acute functional renal failure. Numerous advances in peri-operative management, particularly early rehabilitation, have made it possible to decrease POI. Despite this, the rate of prolonged POI ileus remains high and can be as high as 25% of patients in colorectal surgery. From a pathophysiological point of view, POI has two phases, an early neurological phase and a later inflammatory phase, to which we could add a "pharmacological" phase during which analgesic drugs, particularly opiates, play a central role. The aim of this review article is to describe the phases of the pathophysiology of POI, to analyse the pharmacological treatments currently available through published clinical trials and finally to discuss the different research areas for potential pharmacological targets.

Peri-operative Inflammatory Marker as a Predictive Factor for Prolonged Post-operative Ileus After Gastrectomy for Gastric Cancer

Background/Aims

Although prolonged post-operative ileus (PPOI) is an important factor for the prolonged length of post-operative hospital stay, there is still a lack of effective predictive and therapeutic methods for PPOI. Previous studies reported that increased inflammatory markers, such as C-reactive protein (CRP) level and neutrophil to lymphocyte ratio (NLR), are associated with malignancies. The aim of our study is to elucidate the association between peri-operative inflammatory markers and PPOI after gastrectomy for gastric cancer.

Methods

We enrolled patients who received gastrectomy for gastric cancer from June 2013 to January 2016 at a single tertiary referral center in Seoul, Korea. We evaluated peri-operative inflammatory markers, including CRP level, NLR, and platelet to lymphocyte ratio (PLR) of enrolled patients. We compared these data between control group and PPOI group.

Results

A total of 390 subjects were enrolled in this study, and 132 patients (33.8%) showed PPOI. In univariate analysis, preoperative CRP level and NLR, post-operative day (POD) 1 CRP level, NLR, and PLR, and POD3 CRP level, NLR, and PLR were significantly associated with PPOI. In multivariate analysis, preoperative NLR (P = 0.014), POD1 NLR (P = 0.019), POD3 CRP (P = 0.004), and POD3 NLR (P = 0.008) were independent risk factors for PPOI.

Conclusions

Peri-operative inflammatory markers, such as CRP level and NLR, are useful predictive factors for PPOI who received gastrectomy for gastric cancer. Moreover, prophylactic antibiotics and anti-inflammatory drugs can be preventive and therapeutic agents for PPOI.

Postoperative Ileus: Comparative Pathophysiology and Future Therapies

Postoperative ileus (POI), a decrease in gastrointestinal motility after surgery, is an important problem facing human and veterinary patients. 37.5% of horses that develop POI following small intestinal (SI) resection will not survive to discharge. The two major components of POI pathophysiology are a neurogenic phase which is then propagated by an inflammatory phase. Perioperative care has been implicated, namely the use of opioid therapy, inappropriate fluid therapy and electrolyte imbalances. Current therapy for POI variably includes an early return to feeding to induce physiological motility, reducing the inflammatory response with agents such as non-steroidal anti-inflammatory drugs (NSAIDs), and use of prokinetic therapy such as lidocaine. However, optimal management of POI remains controversial. Further understanding of the roles of the gastrointestinal microbiota, intestinal barrier function, the post-surgical inflammatory response, as well as enteric glial cells, a component of the enteric nervous system, in modulating postoperative gastrointestinal motility and the pathogenesis of POI may provide future targets for prevention and/or therapy of POI.

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.

DA-DRD5 signaling controls colitis by regulating colonic M1/M2 macrophage polarization

The decrease of neurotransmitter dopamine (DA) levels in the intestine is closely related to the development of inflammatory bowel disease (IBD). However, the functional relevance and underlying mechanistic basis of the effects of DA signaling on IBD remains unclear. Here, we observed that the DRD5 receptor is highly expressed in colonic macrophages, and the deficiency of DA-DRD5 signaling exacerbated experimental colitis. Moreover, DA-DRD5 signaling can inhibit M1 by negatively regulating NF-κB signaling but promote M2 macrophage polarization through activation of the CREB pathway, respectively. The deficiency of DRD5 signaling increased colonic M1 macrophages but reduced M2 cells during colitis. Additionally, the administration of a D1-like agonist that has a higher affinity to DRD5 can attenuate the colitogenic phenotype of mice. Collectively, these findings provide the first demonstration of DA-DRD5 signaling in colonic macrophages controlling the development of colitis by regulating M1/M2 macrophage polarization.

Erythropoietin promotes functional recovery in a mouse model of postoperative ileus

BACKGROUND

Dysmotility and postoperative ileus (POI) are major clinical problems after surgical trauma and it is associated with increased intestinal inflammation and oxidative stress. Despite the high occurrence of POI following intra-abdominal surgeries, no effective treatment is currently available. Erythropoietin (EPO) is a multifunctional tissue-protective cytokine with potent anti-inflammatory and anti-oxidative properties, and it is an FDA approved medicine for clinical use. While both EPO and EPO receptors (EPOR) are widely expressed in the gut, the role of EPO in POI is largely unknown. This study was designed to explore the possible beneficial effect of EPO in a mouse model of POI.

METHODS

Mice were subjected to intestinal manipulation to induce standard POI and intestinal transit time was determined at 24-h post-injury with or without EPO treatment (5000 units/kg, once, IP, immediately after intestinal trauma). Intestinal samples were harvested for histological and immunohistochemical analysis.

RESULTS

Systemic EPO significantly improved intestinal transit time compared with control group and it was associated with significantly increased levels of tissue macrophages and reduced levels of oxidative stress.

CONCLUSIONS AND INFERENCES

This is the first pre-clinical study to document novel beneficial effects of EPO in gut dysmotility and our findings suggest that the beneficial effects of EPO in POI is predominantly mediated by its anti-oxidative and immunomodulatory properties.

Experimental postoperative ileus: is Th2 immune response involved?

Rationale: Postoperative ileus (POI) is a frequent complication arising after gastrointestinal surgery but pathogenesis of POI is still not fully understood. While Th1 immune cells are implicated in POI, the involvement of Th2 cells has not yet been clarified. Given the impact of reactive oxygen species (ROS) in the regulation of Th1 and Th2 balance, we hypothesized that not only Th1 but also Th2 immune response can be involved in the development of experimental POI. Methods: The intestinal transit test was performed using carbon gum arabic. Electron microscopy was employed to assess tissue morphology and the presence of immune cells. Cytokines, IgE and ROS were measured. Immune cells from Peyer's patches were analyzed by Flow Cytometry and toluidine blue staining was used for detection of mast cells. Transcriptional factors were analyzed by Western blot. Results: POI is associated with an increase in both Th2 cytokines and Th2 cells. We have further demonstrated that POI induces a Th2-dependent activation of memory and non-memory B cells. This was accompanied by an increase in a number of mast cells in the colon of POI mice as well by an increased IgE and histamine plasma levels. We found that POI-induced accumulation of ROS was associated with an increased expression of the transcriptional factors HMBGI, NF-κB, and p38. This increased expression seemed to be associated with a Th2 response. Conclusion: Th2 immune response can be involved in the activation of mast cells in POI, which was associated with ROS mediated activation of NF-κB and p38 MAPK signaling pathway.

Postoperative Ileus and Postoperative Gastrointestinal Tract Dysfunction: Pathogenic Mechanisms and Novel Treatment Strategies Beyond Colorectal Enhanced Recovery After Surgery Protocols

Postoperative ileus (POI) and postoperative gastrointestinal tract dysfunction (POGD) are well-known complications affecting patients undergoing intestinal surgery. GI symptoms include nausea, vomiting, pain, abdominal distention, bloating, and constipation. These iatrogenic disorders are associated with extended hospitalizations, increased morbidity, and health care costs into the billions and current therapeutic strategies are limited. This is a narrative review focused on recent concepts in the pathogenesis of POI and POGD, pipeline drugs or approaches to treatment. Mechanisms, cellular targets and pathways implicated in the pathogenesis include gut surgical manipulation and surgical trauma, neuroinflammation, reactive enteric glia, macrophages, mast cells, monocytes, neutrophils and ICC's. The precise interactions between immune, inflammatory, neural and glial cells are not well understood. Reactive enteric glial cells are an emerging therapeutic target that is under intense investigation for enteric neuropathies, GI dysmotility and POI. Our review emphasizes current therapeutic strategies, starting with the implementation of colorectal enhanced recovery after surgery protocols to protect against POI and POGD. However, despite colorectal enhanced recovery after surgery, it remains a significant medical problem and burden on the healthcare system. Over 100 pipeline drugs or treatments are listed in Clin.Trials.gov. These include 5HT4R agonists (Prucalopride and TAK 954), vagus nerve stimulation of the ENS-macrophage nAChR cholinergic pathway, acupuncture, herbal medications, peripheral acting opioid antagonists (Alvimopen, Methlnaltexone, Naldemedine), anti-bloating/flatulence drugs (Simethiocone), a ghreline prokinetic agonist (Ulimovelin), drinking coffee, and nicotine chewing gum. A better understanding of the pathogenic mechanisms for short and long-term outcomes is necessary before we can develop better prophylactic and treatment strategies.

Cytokines in abdominal exudate and serum predict small bowel obstruction following appendectomy

BACKGROUND

This study aimed to investigate the value of inflammatory markers for the prediction of small bowel obstruction (SBO) following appendectomy.

METHODS

We included cases of acute appendicitis that underwent laparoscopic appendectomy (LA) in the Qingdao Municipal Hospital between January 2017 and January 2019. The cases were divided into an SBO group and a non-SBO group depending on whether patients had or did not have SBO, and patients were followed up for at least 1 year. The levels of interleukin (IL)-1β, IL-6 and tumour necrosis factor-alpha (TNF-α) in abdominal exudate and venous blood were examined using enzyme-linked immunosorbent assay.

RESULTS

After 1 year of follow-up, there were 985 cases in the non-SBO group and 16 cases in the SBO group. The levels of IL-1β, IL-6 and TNF-α in abdominal exudate on post-operative day 1 in the SBO group were 172.5 ± 14.7, 2167.3 ± 372.1 and 253.9 ± 12.9 pg/mL, respectively, which were significantly higher than that in the non-SBO group. The serum levels of IL-1β, IL-6, TNF-α and C-reactive protein (CRP) in the SBO group were significantly higher than that in the non-SBO group before surgery. Post-operatively, the inflammatory markers above decreased significantly and became similar with time in both groups. The logistic regression showed that the levels of peritoneal IL-6, preoperative serum CRP and perforated appendicitis were significant risk factors of SBO. The specificity and sensitivity of peritoneal IL-6 were 0.81 and 0.921, respectively.

CONCLUSION

The IL-1β, IL-6, TNF-α and CRP in serum and abdominal exudate played an important role in SBO after LA. The peritoneal IL-6 was the most reliable prediction marker for SBO.

Interleukin-10 and Zonulin Are Associated With Postoperative Delayed Gastric Emptying in Critically Ill Surgical Pediatric Patients: A Prospective Pilot Study

Background

Impaired gastric emptying (GE) is associated with morbidity in surgical critically ill children. The relationship between inflammation, gut barrier integrity (lipopolysaccharide binding protein [LBP]; zonulin), and GE has not been described in this cohort.

Methods

Children ≥2 years of age and requiring critical care after surgery were enrolled. Preoperative and postoperative levels of serum cytokines, LBP, and zonulin, and GE by the acetaminophen absorption test, were measured, allowing patients to serve as their own controls. Postoperative delayed GE was defined as a decrease in GE by ≥20% compared with preoperative GE. The following were examined : comparison between postoperative andpreoperative values, correlations between fold change (postoperative/preoperative) in study variables, and fold change in study variables between patients with and without postoperative delayed GE.

Results

Twenty patients, median age 14 years (12.25, 18), 12 female, were included. Eight of 20 patients had postoperative delayed GE. Postoperative interleukin‐6 (IL‐6), IL‐8, IL‐10, and LBP were increased, and zonulin was decreased (P‐values < .05). Fold change in IL‐10 and zonulin were inversely correlated (ρ −0.618, P = .004). Patients with postoperative delayed GE had greater fold increase in IL‐10 (P = .0159) and fold decrease in zonulin (P = .0160). Five of 7 (71%) patients with both fold increase in IL‐10 and decrease in zonulin had delayed GE.

Conclusion

Postoperative changes in IL‐10 and zonulin were associated with delayed GE in surgical critically ill children, which might suggest a mechanism to for delayed GE in postoperative inflammation and gut barrier dysregulation after surgery.

Intestinal Macrophages in Resolving Inflammation

Macrophages not only regulate intestinal homeostasis by recognizing pathogens to control enteric infections but also employ negative feedback mechanisms to prevent chronic inflammation. Hence, macrophages are intriguing targets for immune-mediated therapies, especially when barrier function in the gut is compromised to trigger aberrant inflammatory responses, most notably during inflammatory bowel diseases. Recently, there has been considerable progress in our understanding of human macrophage biology in different tissues, including the intestines. In this review, we discuss some new findings on the properties of distinct populations of intestinal macrophages, how resolution of inflammation and tissue repair by macrophages could be promoted by type 2 cytokines as well as other therapeutic interventions, and highlight some challenges for translating these findings into the future for this exciting area of immunology research.

Leukocyte-Derived Interleukin-10 Aggravates Postoperative Ileus

Objective: Postoperative ileus (POI) is an inflammation-mediated complication of abdominal surgery, characterized by intestinal dysmotility and leukocyte infiltration into the muscularis externa (ME). Previous studies indicated that interleukin (IL)-10 is crucial for the resolution of a variety of inflammation-driven diseases. Herein, we investigated how IL-10 affects the postoperative ME inflammation and found an unforeseen role of IL-10 in POI. Design: POI was induced by a standardized intestinal manipulation (IM) in C57BL/6 and multiple transgenic mouse strain including C-C motif chemokine receptor 2^-/-, IL-10^-/-, and LysM^cre/IL-10^fl/fl mice. Leukocyte infiltration, gene and protein expression of cytokines, chemokines, and macrophage differentiation markers as well as intestinal motility were analyzed. IL-10 serum levels in surgical patients were determined by ELISA. Results: IL-10 serum levels were increased in patient after abdominal surgery. In mice, a complete or leucocyte-restricted IL-10 deficiency ameliorated POI and reduced the postoperative ME neutrophil infiltration. Infiltrating monocytes were identified as main IL-10 producers and undergo IL-10-dependent M2 polarization. Interestingly, M2 polarization is not crucial to POI development as abrogation of monocyte infiltration did not prevent POI due to a compensation of the IL-10 loss by resident macrophages and neutrophils. Organ culture studies demonstrated that IL-10 deficiency impeded neutrophil migration toward the surgically traumatized ME. This mechanism is mediated by reduction of neutrophil attracting chemokines. Conclusion: Monocyte-derived macrophages are the major IL-10 source during POI. An IL-10 deficiency decreases the postoperative expression of neutrophil-recruiting chemokines, consequently reduces the neutrophil extravasation into the postsurgical bowel wall, and finally protects mice from POI.

Pathophysiology and Treatment of Gastrointestinal Motility Disorders in the Acutely Ill

Gastrointestinal dysmotility causes delayed gastric emptying, enteral feed intolerance, and functional obstruction of the small and large intestine, the latter functional obstructions being frequently termed ileus and Ogilvie syndrome, respectively. In addition to meticulous supportive care, drug therapy may be appropriate in certain situations. There is, however, considerable variation among individuals regarding what gastric residual volume identifies gastric dysmotility and would encourage use of a promotility drug. While the administration of either metoclopramide or erythromycin is supported by evidence it appears that, dual-drug therapy (erythromycin and metoclopramide) reduces the rate of treatment failure. There is a lack of evidence to guide drug therapy of ileus, but neither erythromycin nor metoclopramide appear to have a role. Several drugs, including ghrelin agonists, highly selective 5-hydroxytryptamine receptor agonists, and opiate antagonists are being studied in clinical trials. Neostigmine, when infused at a relatively slow rate in patients receiving continuous hemodynamic monitoring, may alleviate the need for endoscopic decompression in some patients.

Ileocecal Anastomosis Type Significantly Influences Long-Term Functional Status, Quality of Life, and Healthcare Utilization in Postoperative Crohn's Disease Patients Independent of Inflammation Recurrence

OBJECTIVES

Anastomotic reconstruction following intestinal resection in Crohn's disease (CD) may employ side-to-side anastomosis (STSA; anti-peristaltic orientation) or end-to-end anastomosis (ETEA). Our aim was to determine the impact of these two anastomotic techniques on long-term clinical status in postoperative CD patients.

METHODS

We performed a comparative effectiveness study of prospectively collected observational data from consented CD patients undergoing their first or second ileocolonic bowel resection and re-anastomosis between 2008 and 2012, in order to assess the association between anastomosis type and 2-year postoperative quality of life (QoL), healthcare utilization, disease clinical or endoscopic recurrence, use of medications, and need for repeat resection.

RESULTS

One hundred and twenty eight postoperative CD patients (60 STSA and 68 ETEA) were evaluated. At 2 years postoperatively, STSA patients had higher rates of emergency department visits (33.3% vs. 14.7%; P=0.01), hospitalizations (30% vs. 11.8%; P=0.01), and abdominal computed tomography scans (50% vs. 13.2%; P<0.001) with lower QoL (mean short inflammatory bowel disease questionnaire 47.9 vs. 53.4; P=0.007). There was no difference among the two groups in the 30 day surgical complications and 2-year patterns of disease activity, CD medication requirement, endoscopic recurrence, and need for new surgical management (all P > 0.05).

CONCLUSIONS

At 2 years postoperatively, CD patients with ETEA demonstrated better QoL and less healthcare utilization compared with STSA, despite having similar patterns of disease recurrence and CD treatment. These findings suggest that surgical reconstruction of the bowel as an intact tube (ETEA) contribute to improved functional and clinical status in patients with CD.

CCR2-dependent monocyte-derived macrophages resolve inflammation and restore gut motility in postoperative ileus

OBJECTIVE

Postoperative ileus (POI) is assumed to result from myeloid cells infiltrating the intestinal muscularis externa (ME) in patients undergoing abdominal surgery. In the current study, we investigated the role of infiltrating monocytes in a murine model of intestinal manipulation (IM)-induced POI in order to clarify whether monocytes mediate tissue damage and intestinal dysfunction or they are rather involved in the recovery of gastrointestinal (GI) motility.

DESIGN

IM was performed in mice with defective monocyte migration to tissues (C-C motif chemokine receptor 2, Ccr2^{-/ -} mice) and wild-type (WT) mice to study the role of monocytes and monocyte-derived macrophages (MΦs) during onset and resolution of ME inflammation.

RESULTS

At early time points, IM-induced GI transit delay and inflammation were equal in WT and Ccr2 ^-/- mice. However, GI transit recovery after IM was significantly delayed in Ccr2 ^-/- mice compared with WT mice, associated with increased neutrophil-mediated immunopathology and persistent impaired neuromuscular function. During recovery, monocyte-derived MΦs acquire pro-resolving features that aided in the resolution of inflammation. In line, bone marrow reconstitution and treatment with MΦ colony-stimulating factor 1 enhanced monocyte recruitment and MΦ differentiation and ameliorated GI transit in Ccr2 ^-/- mice.

CONCLUSION

Our study reveals a critical role for monocyte-derived MΦs in restoring intestinal homeostasis after surgical trauma. From a therapeutic point of view, our data indicate that inappropriate targeting of monocytes may increase neutrophil-mediated immunopathology and prolong the clinical outcome of POI, while future therapies should be aimed at enhancing MΦ physiological repair functions.

Postoperative Ileus: Pathophysiology, Current Therapeutic Approaches

Postoperative ileus, which develops after each abdominal surgical procedure, is an iatrogenic disorder characterized by a transient inhibition of gastrointestinal motility. Its pathophysiology is complex involving pharmacological (opioids, anesthetics), neural, and immune-mediated mechanisms. The early neural phase, triggered by activation of afferent nerves during the surgical procedure, is short lasting compared to the later inflammatory phase. The latter starts after 3-6 h and lasts several days, making it a more interesting target for treatment. Insight into the triggers and immune cells involved is of great importance for the development of new therapeutic strategies. In this chapter, the pathogenesis and the current therapeutic approaches to treat postoperative ileus are discussed.

Abdominal surgery induced gastric ileus and activation of M1-like macrophages in the gastric myenteric plexus: prevention by central vagal activation in rats

Inflammation plays a role in abdominal surgery (AS)-induced intestinal ileus that is alleviated by electrical vagal stimulation. Intracisternal injection of RX-77368, the stable thyrotropin-releasing hormone agonist, activates dorsal motor nucleus neurons and gastric vagal efferent discharges. We investigated the gastric inflammation induced by AS and the modulation by intracisternal RX-77368 in rats. RX-77368 (50 ng/rat) or saline was injected followed, 1 h later, by laparotomy and small intestinal/cecal manipulation. The sham group had anesthesia alone. After 6 h, gastric emptying (GE) and the inflammation in gastric corpus were determined. AS inhibited GE by 72% vs. control and doubled the number of M1-like macrophage immunoreactive for major histocompatibility complex class II (MHCII; M1 marker) but not for cluster of differentiation 206 (CD206; M2 marker) (MHCII⁺/CD206^-) while there was no change in M2-like macrophages (MHCII^-/CD206⁺). AS increased mRNA levels of interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) by 1.7- and 1.5-fold, respectively, in the gastric submucosa plus muscle layers and the infiltration of neutrophils labeled by myeloperoxidase by 9.5-fold in the muscularis externa. RX-77368 inhibited AS-related gastric changes while not altering these parameters in the sham group. There was a significant negative correlation between GE and IL-1β (r = -0.46), TNF-α (r = -0.44), M1 macrophage (r = -0.82), and neutrophils (r = -0.91). The M2-like macrophages and IL-10 expression were unchanged by AS with intracisternal saline or RX-77368. These data indicate that AS activates gastric M1 macrophages and increases proinflammatory cytokines expression, which are prevented by central vagal activation and may contribute to the correlated dampening of postoperative gastric ileus.NEW & NOTEWORTHY MHCII⁺/CD206^- (M1) and MHCII^-/CD206⁺ (M2) constitute two distinct populations of macrophages that are in close apposition to the cholinergic neurons in the rat gastric myenteric plexus (MP). Abdominal surgery (6 h) activates M1 macrophage leading to inflammation in the gastric MP correlated with the delayed gastric emptying, which was abolished by central vagal stimulation via intracisternal injection of RX-77368. Vagal stimulation linked with the cephalic phase may have potential beneficial effects to curtail postoperative gastric ileus.

Transient receptor potential ankyrin 1 agonists improve intestinal transit in a murine model of postoperative ileus

BACKGROUND

Stimulation of transient receptor potential ankyrin 1 (TRPA1), which abundantly expressed in enterochromaffin cells (ECC), has been reported to exert apparently contradictory results in in vitro contractility and in vivo gastrointestinal (GI) transit evaluations. The pharmaceutical-grade Japanese traditional medicine daikenchuto (TU-100) has been reported to be beneficial for postoperative ileus (POI) and accelerate GI transit in animals and humans. TU-100 was recently shown to increase intestinal blood flow via stimulation of TRPA1 in the epithelial cells of the small intestine (SI).

METHODS

The effects of various TRPA1 agonists on motility were examined in a manipulation-induced murine POI model, in vitro culture of SI segments and an ECC model cell line, RIN-14B.

KEY RESULTS

Orally administered TRPA1 agonists, aryl isothiocyanate (AITC) and cinnamaldehyde (CA), TU-100 ingredients, [6]-shogaol (6S) and γ-sanshool (GS), improved SI transit in a POI model. The effects of AITC, 6S and GS but not CA were abrogated in TRPA1-deficient mice. SI segments show periodic peristaltic motor activity whose periodicity disappeared in TRPA1-deficient mice. TU-100 augmented the motility. AITC, CA and 6S increased 5-HT release from isolated SI segments and the effects of all these compounds except for CA were lost in TRPA1-deficient mice. 6S and GS induced a release of 5-HT from RIN-14B cells in a dose- and TRPA1-dependent manner.

CONCLUSIONS & INFERENCES

Intraluminal TRPA1 stimulation is a potential therapeutic strategy for GI motility disorders. Further investigation is required to determine whether 5-HT and/or ECC are involved in the effect of TRPA1 on motility.

Smooth muscle and neural dysfunction contribute to different phases of murine postoperative ileus

BACKGROUND

Postoperative ileus (POI) is characterized by a transient inhibition of gastrointestinal (GI) motility after abdominal surgery mediated by the inflammation of the muscularis externa (ME). The aim of this study was to identify alterations in the enteric nervous system that may contribute to the pathogenesis of POI.

METHODS

Gastrointestinal transit, contractility of isolated smooth muscle strips and inflammatory parameters were evaluated at different time points (1.5 h to 10 days) after intestinal manipulation (IM) in mice. Immune-labeling was used to visualize changes in myenteric neurons.

KEY RESULTS

Intestinal manipulation resulted in an immediate inhibition of GI transit recovering between 24 h and 5 days. In vitro contractility to K(+) (60 mM) or carbachol (10(-9) to 10(-4) M) was biphasically suppressed over 24 h after IM (with transient recovery at 6 h). The first phase of impaired myogenic contractility was associated with increased expression of TNF-α, IL-6 and IL-1α. After 24 h, we identified a significant reduction in electrical field stimulation-evoked contractions and relaxations, lasting up to 10 days after IM. This was associated with a reduced expression of chat and nos1 genes.

CONCLUSIONS & INFERENCES

Intestinal manipulation induces two waves of smooth muscle inhibition, most likely mediated by inflammatory cytokines, lasting up to 3 days after IM. Further, we here identify a late third phase (>24 h) characterized by impaired cholinergic and nitrergic neurotransmission persisting after recovery of muscle contractility. These findings illustrate that POI results from inflammation-mediated impaired smooth muscle contraction, but also involves a long-lasting impact of IM on the enteric nervous system.

Interleukin 10 Restores Gastric Emptying, Electrical Activity, and Interstitial Cells of Cajal Networks in Diabetic Mice

BACKGROUND & AIMS

Gastroparesis is a complication of diabetes characterized by delayed emptying of stomach contents and accompanied by early satiety, nausea, vomiting, and pain. No safe and reliable treatments are available. Interleukin 10 (IL10) activates the M2 cytoprotective phenotype of macrophages and induces expression of heme oxygenase 1 (HO1) protein. We investigated whether IL10 administration could improve gastric emptying and reverse the associated cellular and electrical abnormalities in diabetic mice.

METHODS

Nonobese diabetic mice with delayed gastric emptying were given either IL10 (0.1-1 μg, twice/day) or vehicle (controls). Stomach tissues were isolated, and sharp microelectrode recordings were made of the electrical activity in the gastric muscle layers. Changes to interstitial cells of Cajal (ICC), reduced nicotinamide adenine dinucleotide phosphate diaphorase, and levels and distribution of HO1 protein were determined by histochemical and imaging analyses of the same tissues.

RESULTS

Gastric emptying remained delayed in vehicle-treated diabetic mice but returned to normal in mice given IL10 (n = 10 mice; P < .05). In mice given IL10, normalization of gastric emptying was associated with a membrane potential difference between the proximal and distal stomach, and lower irregularity and higher frequency of slow-wave activity, particularly in the distal stomach. Levels of HO1 protein were higher in stomach tissues from mice given IL10, and ICC networks were more organized, better connected, and more evenly distributed compared with controls.

CONCLUSIONS

IL10 increases gastric emptying in diabetic mice and has therapeutic potential for patients with diabetic gastroparesis. This response is associated with up-regulation of HO1 and repair of connectivity of ICC networks.

Intrinsic Gastrointestinal Macrophages: Their Phenotype and Role in Gastrointestinal Motility

There is an increasing awareness of the role of macrophages in the regulation and maintenance of gastrointestinal function in health and disease. This work has proceeded in the context of an increased understanding of the complex phenotypic variation in macrophages throughout the body and has revealed previously un-identified roles for macrophages in diseases like gastroparesis, post-operative ileus and inflammatory bowel disease. Opportunities for exploiting the phenotypic modulation of tissue resident macrophages have been identified as possible therapies for some of these diseases. In addition, macrophages are an established component of the innate immune system that can respond to variations and changes in the intestinal microbiome and potentially mediate part of the impact of the microbiota on intestinal health. We reviewed the latest work on novel concepts in defining macrophage phenotype, discuss possible mechanisms of action for tissue-resident macrophages in the gut, address the significance of microbiome effects on macrophage phenotype and review the known and possible roles of macrophages in motility disorders of the gastrointestinal tract.

A role for 12/15-lipoxygenase-derived proresolving mediators in postoperative ileus: protectin DX-regulated neutrophil extravasation

Resolution of inflammation is an active counter-regulatory mechanism involving polyunsaturated fatty acid-derived proresolving lipid mediators. Postoperative intestinal motility disturbances, clinically known as postoperative ileus, occur frequently after abdominal surgery and are mediated by a complex inflammation of the intestinal muscularis externa. Herein, we tested the hypothesis that proresolving lipid mediators are involved in the resolution of postoperative ileus. In a standardized experimental model of postoperative ileus, we detected strong expression of 12/15-lipoxygenase within the postoperative muscularis externa of C57BL/6 mice, predominately located within CX3CR1(+)/Ly6C(+) infiltrating monocytes rather than Ly6G(+) neutrophils. Mass spectrometry analyses demonstrated that a 12/15-lipoxygenase increase was accompanied by production of docosahexaenoic acid-derived lipid mediators, particularly protectin DX and resolvin D2, and their common precursor 17-hydroxy docosahexaenoic acid. Perioperative administration of protectin DX, but not resolvin D2 diminished blood-derived leukocyte infiltration into the surgically manipulated muscularis externa and improved the gastrointestinal motility. Flow cytometry analyses showed impaired Ly6G(+)/Ly6C(+) neutrophil extravasation after protectin DX treatment, whereas Ly6G(-)/Ly6C(+) monocyte numbers were not affected. 12/15-lipoxygenase-deficient mice, lacking endogenous protectin DX synthesis, demonstrated increased postoperative leukocyte levels. Preoperative intravenous administration of a docosahexaenoic acid-rich lipid emulsion reduced postoperative leukocyte infiltration in wild-type mice but failed in 12/15-lipoxygenase-deficient mice mice. Protectin DX application reduced leukocyte influx and rescued 12/15-lipoxygenase-deficient mice mice from postoperative ileus. In conclusion, our results show that 12/15-lipoxygenase mediates postoperative ileus resolution via production of proresolving docosahexaenoic acid-derived protectin DX. Perioperative, parenteral protectin DX or docosahexaenoic acid supplementation, as well as modulation of the 12/15-lipoxygenase pathway, may be instrumental in prevention of postoperative ileus.

Endogenous vagal activation dampens intestinal inflammation independently of splenic innervation in postoperative ileus

Postoperative ileus is encountered by patients undergoing open abdominal surgery and is characterized by intestinal inflammation associated with impaired gastrointestinal motility. We recently showed that inflammation of the gut muscularis triggered activation of the vagal efferent pathway mainly targeting the inflamed zone. In the present study we investigate further the modulatory role of endogenous activation of the vagal motor pathway on the innate immune response. Intestinal or splenic denervation was performed two weeks prior to intestinal manipulation (IM) or laparotomy (L). Twenty-four hour post-surgery, the gastrointestinal transit, immune cell influx, and pro-inflammatory cytokine levels were measured in the gut muscularis. Manipulation of the small intestine led to a delay in intestinal transit, an influx of leukocytes and increased pro-inflammatory cytokine expression. Surgical lesion of the vagal branch that selectively innervates the small intestine did not further delay the intestinal transit but significantly enhanced the expression levels of the pro-inflammatory cytokines IL-1β and IL-6 in the gut muscularis. Splenic denervation did not affect intestinal inflammation or gastrointestinal transit after intestinal manipulation. Our study demonstrates that selective vagotomy, leaving the splenic innervation intact, increases surgery-induced intestinal inflammation. These data suggest that endogenous activation of the vagal efferent pathway by intestinal inflammation directly dampens the local immune response triggered by intestinal manipulation independently of the spleen.

The spleen responds to intestinal manipulation but does not participate in the inflammatory response in a mouse model of postoperative ileus

Background

Postoperative ileus is characterized by a transient impairment of the gastrointestinal motility after abdominal surgery. The intestinal inflammation, triggered by handling of the intestine, is the main factor responsible for the prolonged dysmotility of the gastrointestinal tract. Secondary lymphoid organs of the intestine were identified as essential components in the dissemination of inflammation to the entire gastrointestinal tract also called field effect. The involvement of the spleen, however, remains unclear.

Aim

In this study, we investigated whether the spleen responds to manipulation of the intestine and participates in the intestinal inflammation underlying postoperative ileus.

Methods

Mice underwent Laparotomy (L) or Laparotomy followed by Intestinal Manipulation (IM). Twenty-four hours later, intestinal and colonic inflammation was assessed by QPCR and measurement of the intestinal transit was performed. Analysis of homeostatic chemokines in the spleen was performed by QPCR and splenic cell populations analysed by Flow Cytometry. Blockade of the egress of cells from the spleen was performed by administration of the Sphingosine-1-phosphate receptor 1 (S1P₁) agonist CYM-5442 10 h after L/IM.

Results

A significant decrease in splenic weight and cellularity was observed in IM mice 24 h post-surgery, a phenomenon associated with a decreased splenic expression level of the homeostatic chemokine CCL19. Splenic denervation restored the expression of CCL19 and partially prevented the reduction of splenocytes in IM mice. Treatment with CYM-5442 prevented the egress of splenocytes but did not ameliorate the intestinal inflammation underlying postoperative ileus.

Conclusions

Intestinal manipulation results in two distinct phenomena: local intestinal inflammation and a decrease in splenic cellularity. The splenic response relies on an alteration of cell trafficking in the spleen and is partially regulated by the splenic nerve. The spleen however does not participate in the intestinal inflammation during 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.

Review article: carbon monoxide in gastrointestinal physiology and its potential in therapeutics

BACKGROUND

While carbon monoxide (CO) is a known toxin, it is now recognised that CO is also an important signalling molecule involved in physiology and pathophysiology.

AIMS

To summarise our current understanding of the role of endogenous CO in the regulation of gastrointestinal physiology and pathophysiology, and to potential therapeutic applications of modulating CO.

METHODS

This review is based on a comprehensive search of the Ovid Medline comprehensive database and supplemented by our ongoing studies evaluating the role of CO in gastrointestinal physiology and pathophysiology.

RESULTS

Carbon monoxide derived from haem oxygenase (HO)-2 is predominantly involved in neuromodulation and in setting the smooth muscle membrane potential, while CO derived from HO-1 has anti-inflammatory and antioxidative properties, which protect gastrointestinal smooth muscle from damage caused by injury or inflammation. Exogenous CO is being explored as a therapeutic agent in a variety of gastrointestinal disorders, including diabetic gastroparesis, post-operative ileus, organ transplantation, inflammatory bowel disease and sepsis. However, identifying the appropriate mechanism for safely delivering CO in humans is a major challenge.

CONCLUSIONS

Carbon monoxide is an important regulator of gastrointestinal function and protects the gastrointestinal tract against noxious injury. CO is a promising therapeutic target in conditions associated with gastrointestinal injury and inflammation. Elucidating the mechanisms by which CO works and developing safe CO delivery mechanisms are necessary to refine therapeutic strategies.

The role of lymphoid tissue in the attenuation of the postoperative ileus

Standardized intestinal manipulation (IM) leads to local bowel wall inflammation subsequently spreading over the entire gastrointestinal tract. Previously, we demonstrated that this so-called gastrointestinal field effect (FE) is immune-mediated. The aim of this study was to investigate the role of secondary lymphoid organs [mesenteric lymph nodes (MLN), gut-associated lymphoid tissue (GALT)] in IM-mediated FE by employing mice with deficient secondary lymphoid organs (aly/aly, MLN ex) or by administration of 2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol (FTY720), an immunomodulating agent that inhibits emigration of lymphocytes out of lymphoid organs. Small bowel muscularis, and colonic muscularis from wild-type mice as control, from aly/aly mice, FTY720-treated mice (daily dose of 1.0 mg/kg mouse ip starting 3 days before surgical procedure), and wild-type mice that had undergone removal of mesenteric lymph nodes before IM (MLN ex mice) were obtained after selective IM of the jejunum or sham operation. FE was analyzed by measuring transit time of orally administered fluorescent dextran in the gastrointestinal tract [geometric center (GC) of fluorescent dextran], colonic transit time, infiltration of myeloperoxidase-positive cells, and circular smooth muscle contractility. Furthermore, mRNA levels of inflammatory cytokines [interleukin (IL)-6, tumor necrosis factor (TNF)-α, macrophage inflammatory protein (MIP)-1α] were determined by Taqman-PCR. We observed a significantly reduced upregulation of proinflammatory cytokines (IL-6, TNF-α, MIP-1α) in colonic muscularis of MLN ex mice, aly/aly mice, and FTY720-treated mice compared with wild-type mice. Contractility of circular muscularis strips of the colon but not the jejunum was significantly improved in aly/aly mice and FTY720-treated wild-type mice. Additionally, inflammation of the colon determined by the number of myeloperoxidase-positive cells and colonic transit time were significantly improved in aly/aly mice, FTY720-treated wild-type mice, and in MLN ex mice. In summary, lack of secondary lymphoid organs (MLN + GALT) in aly/aly mice or administration of FTY720 abrogated FE after IM as opposed to wild-type mice. These data demonstrate that secondary lymphoid organs are involved in the propagation of FE and postoperative ileus. FTY720 indirectly affects FE by inhibiting migration of activated T cells from the jejunum and adjacent secondary lymphoid organs to the colon. These findings support the crucial role of the adaptive immune system in FE, most likely by a sphyngosine 1-phosphate-dependent mechanism.

Antioxidants counteract lipopolysaccharide-triggered alterations of human colonic smooth muscle cells

Gut dysmotility develops in individuals during and after recovering from infective acute gastroenteritis and it is apparently due to a direct effect of circulating lipopolysaccharides (LPS). This is an endotoxin with a prooxidant activity derived from gram-negative bacteria. Due to the lack of human models available so far, the mechanisms underlying LPS-induced gut dysmotility are, however, poorly investigated. In the present work long-term effects of LPS and their reversibility have been assessed by means of different analytical cytology methods on pure primary cultures of human colonic smooth muscle cells. We found that LPS triggered the following alterations: (i) a redox imbalance with profound changes of contractile microfilament network, and (ii) the induction of cell cycle progression with dedifferentiation from a contractile to a synthetic phenotype. These alterations persisted also after LPS removal. Importantly, two unrelated antioxidants, alpha-tocopherol and N-acetylcysteine, were able to reverse the cytopathic effects of LPS and to restore normal muscle cell function. The present data indicate that LPS is capable of triggering a persistent and long-term response that could contribute to muscle dysfunction occurring after an infective and related inflammatory burst and suggest a reappraisal of antioxidants in the management of postinfective motor disorders of the gut.

Functional assessment of intestinal motility and gut wall inflammation in rodents: analyses in a standardized model of intestinal manipulation

Inflammation of the gastrointestinal tract is a common reason for a variety of human diseases. Animal research models are critical in investigating the complex cellular and molecular of intestinal pathology. Although the tunica mucosa is often the organ of interest in many inflammatory diseases, recent works demonstrated that the muscularis externa (ME) is also a highly immunocompetent organ that harbours a dense network of resident immunocytes.(1,2) These works were performed within the standardized model of intestinal manipulation (IM) that leads to inflammation of the bowel wall, mainly limited to the ME. Clinically this inflammation leads to prolonged intestinal dysmotility, known as postoperative ileus (POI) which is a frequent and unavoidable complication after abdominal surgery.(3) The inflammation is characterized by liberation of proinflammatory mediators such as IL-6(4) or IL-1β or inhibitory neurotransmitters like nitric oxide (NO).(5) Subsequently, tremendous numbers of immunocytes extravasate into the ME, dominated by polymorphonuclear neutrophils (PMN) and monocytes and finally maintain POI.(2) Lasting for days, this intestinal paralysis leads to an increased risk of aspiration, bacterial translocation and infectious complications up to sepsis and multi organ failure and causes a high economic burden.(6) In this manuscript we demonstrate the standardized model of IM and in vivo assessment of gastrointestinal transit (GIT) and colonic transit. Furthermore we demonstrate a method for separation of the ME from the tunica mucosa followed by immunological analysis, which is crucial to distinguish between the inflammatory responses in these both highly immunoactive bowel wall compartments. All analyses are easily transferable to any other research models, affecting gastrointestinal function.

Immune mediators of postoperative ileus

CLINICAL BACKGROUND: In all patients undergoing abdominal surgery, a transient phase of interruption of bowel motility, named postoperative ileus (POI) occurs. POI is often accepted as an unavoidable "physiological" response and a self-limiting complication after surgery although it has a significant impact on patient morbidity with prolonged hospitalization and increased costs. Annual economic burden has been estimated as much as US $1.47 billion in the USA (Iyer et al. in J Manag Care Pharm 15(6):485-494, 2009).

PATHOPHYSIOLOGY

The pathophysiology has been elucidated within the last decades, demonstrating that both, neurogenic and inflammatory mechanisms are involved in response to the surgical trauma. It is now generally accepted that POI pathogenesis processes in two phases: a first neurogenic phase is accountable for the immediate postoperative impairment of bowel motility. This is followed by a second immunological phase that can last for days and mainly affects strength and length of POI. More recent findings demonstrate a bidirectional interaction between the nervous and the immune system, and this interaction significantly contributed to our present understanding of POI pathophysiology. Although nerval mechanisms have a significant impact in the early phase of POI, the contribution of the immune system and subsequently its manipulation has risen as the most promising strategy in prevention or treatment of the clinically relevant prolonged form of POI.

AIMS

The present manuscript will give an update on the inflammatory responses, the involved cell types, and participating immune mediators in POI.

Hydrogen-enriched preservation protects the isogeneic intestinal graft and amends recipient gastric function during transplantation

BACKGROUND

Inhaled hydrogen gas exerts antioxidant and anti-inflammatory effects in rat intestinal transplantation. Here, we investigated whether ex vivo donor organ treatment with dissolved hydrogen would prevent intestinal graft injury.

METHODS

Isogeneic intestinal transplantation was performed in Lewis rats with vascular flush, luminal preservation, and cold graft storage in nitrogen-bubbled (SITxN2) or hydrogen-bubbled (SITxH2) preservation solution. Lactated Ringer's solution and 3-hr cold ischemia time were used for mechanistic investigations, whereas survival experiments were performed with University of Wisconsin solution and 6-hr cold ischemia time.

RESULTS

During the early phase of ischemia-reperfusion injury, hydrogen-enriched solution significantly preserved mucosal graft morphology, diminished graft malondialdehyde levels demonstrating substantial reduction potential and blunted proinflammatory molecular responses (early growth response gene [EGR-1], interleukin [IL]-6, IL-1ß, and inducible nitric oxide synthase) within the reperfused intestinal graft muscularis. During the late phase of ischemia-reperfusion injury, circulating IL-6 protein and lactate dehydrogenase levels were significantly ameliorated in SITxH2 animals, which were associated with a favorable functional outcome in in vivo liquid gastrointestinal transit and recipient solid gastric emptying of chrome steel balls, and marked prevention of the posttransplant associated suppression of in vitro muscarinic jejunal contractility. Reflecting improved graft preservation, hydrogen preloading of grafts increased recipient survival rates from 41% to 80%. Anti-inflammatory and antiapoptotic heme oxygenase-1 was significantly upregulated in the hydrogen-treated graft muscularis but not mucosa before reperfusion.

CONCLUSIONS

Graft preloading with hydrogen demonstrated superior morphologic and functional graft protection in rodent intestinal transplantation, ultimately facilitating recipient survival. Antioxidant capacity and muscularis heme oxygenase-1 upregulation are possible protective mechanisms.

Nutritional stimulation of the autonomic nervous system

Disturbance of the inflammatory response in the gut is important in several clinical diseases ranging from inflammatory bowel disease to postoperative ileus. Several feedback mechanisms exist that control the inflammatory cascade and avoid collateral damage. In the gastrointestinal tract, it is of particular importance to control the immune response to maintain the balance that allows dietary uptake and utilization of nutrients on one hand, while preventing invasion of bacteria and toxins on the other hand. The process of digestion and absorption of nutrients requires a relative hyporesponsiveness of the immune cells in the gut to luminal contents which is not yet fully understood. Recently, the autonomic nervous system has been identified as an important pathway to control local and systemic inflammation and gut barrier integrity. Activation of the pathway is possible via electrical or via pharmacological interventions, but is also achieved in a physiological manner by ingestion of dietary lipids. Administration of dietary lipids has been shown to be very effective in reducing the inflammatory cascade and maintaining intestinal barrier integrity in several experimental studies. This beneficial effect of nutrition on the inflammatory response and intestinal barrier integrity opens new therapeutic opportunities for treatment of certain gastrointestinal disorders. Furthermore, this neural feedback mechanism provides more insight in the relative hyporesponsiveness of the immune cells in the gut. Here, we will discuss the regulatory function of the autonomic nervous system on the inflammatory response and gut barrier function and the potential benefit in a clinical setting.

Novel model of peripheral tissue trauma-induced inflammation and gastrointestinal dysmotility

BACKGROUND

Trauma is a leading cause of death and although the gut is recognized as the 'motor' of post-traumatic systemic inflammatory response syndrome and multiple organ failure, studies on the gastrointestinal (GI) tract are few. Our objectives were to create a precisely controllable tissue injury model in which GI motility, systemic inflammation and wound fluid can be analyzed.

METHODS

A non-narcotic murine trauma model was developed by the subcutaneous dorsal trans-implantation of a devitalized donor syngeneic harvested tissue-bone matrix (TBX), which was precisely adjusted to % total body weight and studied after 21 h. Gastrointestinal transit histograms were plotted after the oral administration of non-digestible FITC-dextran and geometric centers calculated. Organ bath evaluated jejunal circular muscle contractility. Multiplex electrochemiluminescence measurements of serum and TBX wound fluid inflammatory mediators were performed.

KEY RESULTS

Increasing TBX amounts progressively delayed transit, whereas TBX heat denaturation or decellularization prevented ileus and death. In the TBX(17.5%) model, jejunal muscle contractility was suppressed and a systemic inflammatory response developed as significant serum elevations in IL-6, keratinocyte cytokine and IL-10 compared to sham. In addition, inflammatory responses within the wound fluid showed elevated levels of preformed IL-1β and TNF-α, whereas, 21 h after implantation IL-1β, IL-6 and keratinocyte cytokine were significantly increased in the wound.

CONCLUSIONS & INFERENCES

A novel donor tissue-bone matrix trauma model was developed that is precisely adjustable and recapitulates important clinical phenomena. The non-narcotic model demonstrated that increasing tissue injury progressively caused ileus, initiated a systemic inflammatory response and developed inflammatory changes within the wound.

Interleukin-10 production by tumor infiltrating macrophages plays a role in Human Papillomavirus 16 tumor growth

BACKGROUND

Human Papillomavirus, HPV, is the main etiological factor for cervical cancer. Different studies show that in women infected with HPV there is a positive correlation between lesion grade and number of infiltrating macrophages, as well as with IL-10 higher expression. Using a HPV16 associated tumor model in mice, TC-1, our laboratory has demonstrated that tumor infiltrating macrophages are M2-like, induce T cell regulatory phenotype and play an important role in tumor growth. M2 macrophages secrete several cytokines, among them IL-10, which has been shown to play a role in T cell suppression by tumor macrophages in other tumor models. In this work, we sought to establish if IL-10 is part of the mechanism by which HPV tumor associated macrophages induce T cell regulatory phenotype, inhibiting anti-tumor activity and facilitating tumor growth.

RESULTS

TC-1 tumor cells do not express or respond to IL-10, but recruit leukocytes which, within the tumor environment, produce this cytokine. Using IL-10 deficient mice or blocking IL-10 signaling with neutralizing antibodies, we observed a significant reduction in tumor growth, an increase in tumor infiltration by HPV16 E7 specific CD8 lymphocytes, including a population positive for Granzyme B and Perforin expression, and a decrease in the percentage of HPV specific regulatory T cells in the lymph nodes.

CONCLUSIONS

Our data shows that in the HPV16 TC-1 tumor mouse model, IL-10 produced by tumor macrophages induce regulatory phenotype on T cells, an immune escape mechanism that facilitates tumor growth. Our results point to a possible mechanism behind the epidemiologic data that correlates higher IL-10 expression with risk of cervical cancer development in HPV infected women.

Controlling postoperative ileus by vagal activation

Postoperative ileus is a frequently occurring surgical complication, leading to increased morbidity and hospital stay. Abdominal surgical interventions are known to result in a protracted cessation of bowel movement. Activation of inhibitory neural pathways by nociceptive stimuli leads to an inhibition of propulsive activity, which resolves shortly after closure of the abdomen. The subsequent formation of an inflammatory infiltrate in the muscular layers of the intestine results in a more prolonged phase of ileus. Over the last decade, clinical strategies focusing on reduction of surgical stress and promoting postoperative recovery have improved the course of postoperative ileus. Additionally, recent experimental evidence implicated antiinflammatory interventions, such as vagal stimulation, as potential targets to treat postoperative ileus and reduce the period of intestinal hypomotility. Activation of nicotinic receptors on inflammatory cells by vagal input attenuates inflammation and promotes gastrointestinal motility in experimental models of ileus. A novel physiological intervention to activate this neuroimmune pathway is enteral administration of lipid-rich nutrition. Perioperative administration of lipid-rich nutrition reduced manipulation-induced local inflammation of the intestine and accelerated recovery of bowel movement. The application of safe and easy to use antiinflammatory interventions, together with the current multimodal approach, could reduce postoperative ileus to an absolute minimum and shorten hospital stay.

Schistosoma mansoni proteins attenuate gastrointestinal motility disturbances during experimental colitis in mice

AIM: To investigate the therapeutic effect of Schistosoma mansoni (S. mansoni) soluble worm proteins on gastrointestinal motility disturbances during experimental colitis in mice.

METHODS: Colitis was induced by intrarectal injection of trinitrobenzene sulphate (TNBS) and 6 h later, mice were treated ip with S. mansoni proteins. Experiments were performed 5 d after TNBS injection. Inflammation was quantified using validated inflammation parameters. Gastric emptying and geometric center were measured to assess in vivo gastrointestinal motility. Peristaltic activity of distal colonic segments was studied in vitro using a modified Trendelenburg set-up. Cytokine profiles of T-lymphocytes isolated from the colon were determined by real time reverse transcriptase-polymerase chain reaction.

RESULTS: Intracolonic injection of TNBS caused severe colitis. Treatment with S. mansoni proteins significantly ameliorated colonic inflammation after 5 d. TNBS did not affect gastric emptying but significantly decreased the geometric center and impaired colonic peristaltic activity 5 d after the induction of colitis. Treatment with S. mansoni proteins ameliorated these in vivo and in vitro motility disturbances. In addition, TNBS injection caused a downregulation of effector T cell cytokines after 5 d, whereas a S. mansoni protein effect was no longer observed at this time point.

CONCLUSION: Treatment with S. mansoni proteins attenuated intestinal inflammation and ameliorated motility disturbances during murine experimental colitis.

Dietary plasma protein supplements prevent the release of mucosal proinflammatory mediators in intestinal inflammation in rats

Spray-dried plasma (SDP) is a complex mixture of active proteins that modulates the immune response of gut-associated lymphoid tissue. We examined whether SDP and Ig concentrate (IC) supplementation could modulate cytokine expression and inflammatory mediators in rats challenged with Staphylococcus aureus enterotoxin B (SEB). Wistar-Lewis rats were fed diets supplemented with SDP (8% wt:wt), IC (1.5% wt:wt), or milk proteins (control diet) from weaning (d 21) to d 34 after birth. On d 32 and 35, the rats were given SEB (0.5 mg/kg; intraperitoneal). Six hours after the second SEB dose, jejunal mucosa and Peyer's patches (PP) from the small intestine were collected. The cytokines interferon-gamma (IFNgamma), tumor necrosis factor-alpha (TNFalpha), interleukin (IL)-6, IL-10, transforming growth factor-beta (TGFbeta), and leukotrienne B(4) (LTB(4)) were analyzed using commercial kits. SEB increased the release of proinflammatory mediators (IFNgamma, TNFalpha, IL-6, and LTB(4)) in PP (P < 0.05) and in the mucosa (P < 0.05). In both tissues, SDP prevented the increase in IFNgamma, IL-6, and LTB(4) induced by SEB (P < 0.05). IC reduced the expression of TNFalpha and LTB(4) in PP and mucosa (P < 0.05). SDP supplementation increased IL-10 and mature TGFbeta concentrations in intestinal mucosa from both inflamed and noninflamed rats. Both SDP and IC increased the mature:total TGFbeta ratio (all P < 0.05). Both supplements were effective at preventing the SEB-induced increase in proinflammatory:antiinflammatory cytokine ratios in PP and mucosa and in serum. The preventive effects of plasma supplements on intestinal inflammation involve modulation of intestinal cytokines, characterized by an increased expression of antiinflammatory cytokines.