T helper type 1 memory cells disseminate postoperative ileus over the entire intestinal tract

Postoperative recovery of colorectal patients enhanced with dexmedetomidine (PReCEDex): a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Intraoperative administration of dexmedetomidine has shown promise in improving postoperative gastrointestinal function. In the context of colorectal surgery, the results remain inconsistent. This review aims to provide a synthesis of studies assessing the effect of dexmedetomidine on postoperative gastrointestinal function in colorectal surgery patients.

METHODS

CENTRAL, Emcare, Embase, and MEDLINE were searched up to September 2023. Randomized controlled trials involving adult patients (≥ 18 years) undergoing elective colorectal surgery, comparing dexmedetomidine administration to a control group, and reporting on postoperative gastrointestinal function were included. Non-comparative and emergent procedures were excluded. Primary outcome was time to first flatus or bowel movement, and secondary outcomes included length of stay and time to solid oral intake. Risk of bias was assessed using the Cochrane risk of bias tool for randomized studies.

RESULTS

After screening 1194 citations, eight studies were included. Studies comprised of 570 patients in the dexmedetomidine group (mean age: 65.8 years, 43% female, mean BMI: 22.7 kg/m2) and 556 patients in control group (mean age 70.6 years, 40% female, mean BMI 22.5 kg/m2). Dexmedetomidine administration resulted in a shorter time to flatus (MD -4.55 h, 95% CI: 20.14-8.95, p < 0.005, very low certainty of evidence), a shorter time to first bowel movement (MD -11.9 h, 95% CI: 18.74-5.05, p < 0.005, very low certainty of evidence), a shorter time to solid oral intake (MD -4.34 h, 95% CI: 17.43-11.24, p < 0.005, moderate certainty of evidence), and a shorter length of stay (MD -.06 days, 95% CI: 1.99-0.12, p < 0.05, very low certainty of evidence).

CONCLUSION

In adult patients undergoing elective colorectal surgery, intraoperative use of dexmedetomidine results in clinically meaningful improvements in postoperative gastrointestinal function and consequently, shorter length of stay. Therefore, dexmedetomidine may serve as a valuable adjunct in enhancing postoperative recovery of patients following elective colorectal surgery, thereby reducing healthcare utilization, and improving patient outcomes.

Global research trends in postoperative ileus from 2011 to 2023: A scientometric study

BACKGROUND

Postoperative ileus (POI) is a common complication after abdominal surgery with high morbidity, which hinders patient recovery, prolongs hospitalization, and increases healthcare costs. Therefore, POI has become a global public health challenge. POI triggering is multifactorial. Autonomic and hormonal mechanisms are generally involved in POI pathogenesis. Recent studies have shown that beta adrenergic signaling of enteric glia is a POI trigger. Currently, the status quo, trends, and frontiers of global research on POI remain unclear.

AIM

To explore the current status, trends, and frontiers of POI research from 2011 to the present based on bibliometric analysis.

METHODS

Publications published on POI research from 2011 to 2023 were retrieved on June 1, 2023, from the Web of Science Core Collection. CiteSpace 6.2.R2 and VOSviewer were used to conduct bibliometric visualization.

RESULTS

In total, 778 POI records published from 2011 to 2023 were retrieved. Over the past few decades, the annual cumulative number of related articles has linearly increased, with China and the United States of America contributing prominently. All publications were from 59 countries and territories. China and the University of Bonn were the top contributing country and institution, respectively. Neurogastroenterology & Motility was the most prolific journal. The Journal of Gastrointestinal Surgery had the highest number of citations. Wehner Sven was the most productive author. Burst keywords (e.g., colon, prolonged ileus, acupuncture, paralytic ileus, pathophysiology, rectal cancer, gastrointestinal function, risk) and a series of reference citation bursts provided evidence for the research frontiers in recent years.

CONCLUSION

This study demonstrates trends in the published literature on POI and provides new insights for researchers. It emphasizes the importance of multidisciplinary cooperation in the development of this field.

Electroacupuncture treatment improves postoperative ileus by inhibiting the Th1 cell-mediated inflammatory response through the vagus nerve

BACKGROUND

Electroacupuncture (EA) has been reported to improve intestinal motility in mice with postoperative ileus (POI). Previous studies, however, have yielded heterogeneous results regarding the effect of EA on POI.

METHODS

Herein, a POI mouse model was constructed by intestinal manipulation. To evaluate the effect of EA treatment on colonic transit, the levels of inflammatory markers (macrophage inflammatory protein (MIP)-1α, interleukin (IL)-1β, IL-6, monocyte chemotactic protein (MCP)-1 and intercellular adhesion molecule (ICAM)-1) were detected by enzyme-linked immunosorbent assay (ELISA); immune cell infiltration was detected by immunohistochemical staining of myeloperoxidase (MPO), ectodysplasin (ED)-1 and ED-2, and the percentage of CD4+ interferon (IFN)-γ+ Th1 cells and IFN-γ secretion levels were determined. Activated Th1 cells and pentoxifylline, a cell differentiation inhibitor, were used to assess the role of Th1 cells in EA treatment of POI. Neostigmine administration and unilateral vagotomy were performed to confirm whether the effects of EA treatment on Th1 cells were mediated by the vagus nerve (VN).

RESULTS

The results revealed that EA treatment at ST36 improved POI, as indicated by a decreased level of inflammatory-related markers and immune cell infiltration and shortened colonic transit time. The activated Th1 cells abolished the effects of EA treatment on POI. The effects of EA treatment on POI were enhanced by stimulation of the VN along with a decreased level of Th1 cells, but these effects were abolished by vagotomy along with an increased percentage of Th1 cells; this result indicates that the VN mediates the role of Th1 cells in the effects of EA treatment of POI.

CONCLUSION

Our findings showed that the effects of EA treatment of POI were mainly mediated by Th1 cells through the stimulation of the VN and inhibition of the inflammatory response.

Role of ICAM-1 in the Adhesion of T Cells to Enteric Glia: Perspectives in the Formation of Plexitis in Crohn's Disease

BACKGROUND & AIMS

The presence of myenteric plexitis in the proximal resection margins is a predictive factor of early postoperative recurrence in Crohn's disease. To decipher the mechanisms leading to their formation, T-cell interactions with enteric neural cells were studied in vitro and in vivo.

METHODS

T cells close to myenteric neural cells were retrospectively quantified in ileocolonic resections from 9 control subjects with cancer and 20 patients with Crohn's disease. The mechanisms involved in T-cell adhesion were then investigated in co-cultures of T lymphocytes with enteric glial cells (glia). Finally, the implication of adhesion molecules in the development of plexitis and colitis was studied in vitro but also in vivo in Winnie mice.

RESULTS

The mean number of T cells close to glia, but not neurons, was significantly higher in the myenteric ganglia of relapsing patients with Crohn's disease (2.42 ± 0.5) as compared with controls (0.36 ± 0.08, P = .0007). Co-culture experiments showed that exposure to proinflammatory cytokines enhanced T-cell adhesion to glia and increased intercellular adhesion molecule-1 (ICAM-1) expression in glia. We next demonstrated that T-cell adhesion to glia was inhibited by an anti-ICAM-1 antibody. Finally, using the Winnie mouse model of colitis, we showed that the blockage of ICAM-1/lymphocyte function-associated antigen-1 (LFA-1) with lifitegrast reduced colitis severity and decreased T-cell infiltration in the myenteric plexus.

CONCLUSIONS

Our present work argues for a role of glia-T-cell interaction in the development of myenteric plexitis through the adhesion molecules ICAM-1/LFA-1 and suggests that deciphering the functional consequences of glia-T-cell interaction is important to understand the mechanisms implicated in the development and recurrence of Crohn's disease.

Effect of the gut microbiota and their metabolites on postoperative intestinal motility and its underlying mechanisms

Gut microbiota is closely related to human health and disease because, together with their metabolites, gut microbiota maintain normal intestinal peristalsis. The use of antibiotics or opioid anesthetics, or both, during surgical procedures can lead to dysbiosis and affect intestinal motility; however, the underlying mechanisms are not fully known. This review aims to discuss the effect of gut microbiota and their metabolites on postoperative intestinal motility, focusing on regulating the enteric nervous system, 5-hydroxytryptamine neurotransmitter, and aryl hydrocarbon receptor.

Stretch-Induced Down-Regulation of HCN2 Suppresses Contractile Activity

Although hyperpolarization-activated and cyclic nucleotide-gated 2 channels (HCN2) are expressed in multiple cell types in the gut, the role of HCN2 in intestinal motility is poorly understood. HCN2 is down-regulated in intestinal smooth muscle in a rodent model of ileus. Thus, the purpose of this study was to determine the effects of HCN inhibition on intestinal motility. HCN inhibition with ZD7288 or zatebradine significantly suppressed both spontaneous and agonist-induced contractile activity in the small intestine in a dose-dependent and tetrodotoxin-independent manner. HCN inhibition significantly suppressed intestinal tone but not contractile amplitude. The calcium sensitivity of contractile activity was significantly suppressed by HCN inhibition. Inflammatory mediators did not affect the suppression of intestinal contractile activity by HCN inhibition but increased stretch of the intestinal tissue partially attenuated the effects of HCN inhibition on agonist-induced intestinal contractile activity. HCN2 protein and mRNA levels in intestinal smooth muscle tissue were significantly down-regulated by increased mechanical stretch compared to unstretched tissue. Increased cyclical stretch down-regulated HCN2 protein and mRNA levels in primary human intestinal smooth muscle cells and macrophages. Overall, our results suggest that decreased HCN2 expression induced by mechanical signals, such as intestinal wall distension or edema development, may contribute to the development of ileus.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Inflammation and Impaired Gut Physiology in Post-operative Ileus: Mechanisms and the Treatment Options

Post-operative ileus (POI) is the transient cessation of coordinated gastrointestinal motility after abdominal surgical intervention. It decreases quality of life, prolongs length of hospital stay, and increases socioeconomic costs. The mechanism of POI is complex and multifactorial, and has been broadly categorized into neurogenic and inflammatory phase. Neurogenic phase mediated release of corticotropin-releasing factor (CRF) plays a central role in neuroinflammation, and affects both central autonomic response as well hypothalamic-pituitary-adrenal (HPA) axis. HPA-stress axis associated cortisol release adversely affects gut microbiota and permeability. Peripheral CRF (pCRF) is a key player in stress induced gastric emptying and colonic transit. It functions as a local effector and interacts with the CRF receptors on the mast cell to release chemical mediators of inflammation. Mast cells proteases disrupt epithelial barrier via protease activated receptor-2 (PAR-2). PAR-2 facilitates cytoskeleton contraction to reorient tight junction proteins such as occludin, claudins, junctional adhesion molecule, and zonula occludens-1 to open epithelial barrier junctions. Barrier opening affects the selectivity, and hence permeation of luminal antigens and solutes in the gastrointestinal tract. Translocation of luminal antigens perturbs mucosal immune system to further exacerbate inflammation. Stress induced dysbiosis and decrease in production of short chain fatty acids add to the inflammatory response and barrier disintegration. This review discusses potential mechanisms and factors involved in the pathophysiology of POI with special reference to inflammation and interlinked events such as epithelial barrier dysfunction and dysbiosis. Based on this review, we recommend CRF, mast cells, macrophages, and microbiota could be targeted concurrently for efficient POI management.

Impact of intravenous dexmedetomidine on gastrointestinal function recovery after laparoscopic hysteromyomectomy: a randomized clinical trial

Postoperative intestinal ileus is common after laparoscopic surgery, the incidence of those after hysterectomy was 9.2%. Anesthesia is one of the independent risk factors of postoperative ileus. Dexmedetomidine has been widely used in perioperative anesthesia and previous reports suggested that intraoperative dexmedetomidine may be associated with the improvement of gastrointestinal function recovery after abdominal surgery. We hypothesized that dexmedetomidine could improve gastrointestinal function recovery after laparoscopic hysteromyomectomy. Participants in elective laparoscopic hysteromyomectomy were enrolled with a single dose of 0.5 μg kg⁻¹ dexmedetomidine or the same volume of placebo intravenously administered for 15 min, followed by continuous pumping of 0.2 μg kg⁻¹ h⁻¹ of corresponding drugs until 30 min before the end of surgery. The primary outcome was the time to first flatus. Secondary outcomes were the time to first oral feeding and the first defecation, the occurrence of flatulence, pain score and postoperative nausea and vomiting until 48 h after the surgery. Eventually, 106 participants (54 in dexmedetomidine group and 52 in placebo group) were included for final analysis. The time to first flatus (SD, 25.83 [4.18] vs 27.67 [3.77], P = 0.019), oral feeding time (SD, 27.29 [4.40] vs 28.92 [3.82], P = 0.044), the time to first defecation (SD, 59.82 [10.49] vs 63.89 [7.71], P = 0.025), abdominal distension (n%, 12 (22.2) vs 21 (40.4), P = 0.044), PONV at 24 h (n%, 10 (18.5) vs 19 (36.5), P = 0.037), NRS 6 h (3.15(0.68) vs 3.46 (0.87), P = 0.043) and NRS 12 h (3.43 (0.88) vs 3.85 (0.85), P = 0.014) of dexmedetomidine group were significantly shorter than those of the placebo group. Intraoperative dexmedetomidine reduced the time to first flatus, first oral feeding, and first defecation. These results suggested that this treatment may be a feasible strategy for improving postoperative gastrointestinal function recovery in patients undergoing laparoscopic hysteromyomectomy.

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.

The Role of Inflammatory Mediators in the Development of Gastrointestinal Motility Disorders

Feeding intolerance and the development of ileus is a common complication affecting critically ill, surgical, and trauma patients, resulting in prolonged intensive care unit and hospital stays, increased infectious complications, a higher rate of hospital readmission, and higher medical care costs. Medical treatment for ileus is ineffective and many of the available prokinetic drugs have serious side effects that limit their use. Despite the large number of patients affected and the consequences of ileus, little progress has been made in identifying new drug targets for the treatment of ileus. Inflammatory mediators play a critical role in the development of ileus, but surprisingly little is known about the direct effects of inflammatory mediators on cells of the gastrointestinal tract, and many of the studies are conflicting. Understanding the effects of inflammatory cytokines/chemokines on the development of ileus will facilitate the early identification of patients who will develop ileus and the identification of new drug targets to treat ileus. Thus, herein, we review the published literature concerning the effects of inflammatory mediators on gastrointestinal motility.

Purinergic P2X7 receptor antagonist ameliorates intestinal inflammation in postoperative ileus

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

Activation of p38 mitogen-activated protein kinase pathway by lipopolysaccharide aggravates postoperative ileus in colorectal cancer patients

BACKGROUND AND AIM

Patients undergoing abdominal surgery can develop postoperative ileus (POI). Inflammation of the intestinal muscularis following intestinal manipulation may be caused by displaced bacteria or lipopolysaccharide (LPS). The aim of this study was to investigate the relationship between gut microbiota, LPS, and POI in colorectal cancer (CRC) patients and explore underlying mechanisms of LPS-triggered POI.

METHODS

Sixty CRC patients undergoing colorectal resection were included. Bacterial communities from fecal samples were characterized by 16S rRNA gene sequencing, and fecal LPS levels were determined by Limulus amebocyte lysate assay. Mice were used to mechanistically investigate the causal relationship between microbiota, LPS, and POI.

RESULTS

We discovered that CRC patients who developed prolonged POI (PPOI) had a unique pro-inflammatory gut microbial composition during the perioperative period. The highest proportions of Gram-negative bacteria at the genus level were Escherichia-Shigella and Bacteroides; the abundance of Escherichia-Shigella was higher throughout the perioperative period. Fecal LPS levels were significantly higher in patients with PPOI. In mice treated with an antibiotic cocktail, intestinal muscularis inflammation and intestinal dysfunction were significantly improved. Inflammation and dysfunction were significantly reduced in mice treated with polymyxin B, but were worsened by treatment with LPS. Moreover, LPS upregulated p38 phosphorylation in mice, and treatment with an inhibitor of p38 (SB203580) significantly alleviated intestinal inflammation and dysmotility.

CONCLUSION

Lipopolysaccharide increases intestinal muscularis inflammation via activation of p38 signaling, which aggravates POI. Removing bacterial sources of LPS during the perioperative period is promising for the prophylactic treatment of PPOI.

Post-operative ileus: definitions, mechanisms and controversies

Post-operative ileus (POI) is a syndrome of impaired gastrointestinal transit which occurs following abdominal surgery. There are few effective targeted therapies for ileus, and research has been limited by inconsistent definitions and an incomplete understanding of the underlying pathophysiology. Despite considerable effort, there remains no widely-adopted definition of ileus, and recent work has identified variation in outcome reporting is a major source of heterogeneity in clinical trials. Outcomes should be clearly-defined, clinically-relevant, and reflective of the underlying biology, impacts on hospital resources and quality of life. Further collaborative efforts will be needed to develop consensus definitions and a core outcome set for postoperative gastrointestinal recovery. Investigation into the pathophysiology of POI has been hindered by use of low-resolution techniques and difficulties linking cellular mechanisms to dysmotility patterns and clinical symptoms. Recent evidence has suggested the common assumption of post-operative GI paralysis is incorrect, and that the distal colon becomes hyperactive following surgery. The post-operative inflammatory response is important in the pathophysiology of ileus, but the time course of this in humans remains unclear, with the majority of evidence coming from animal models. Future work should investigate dysmotility patterns underlying ileus, and identify biomarkers which may be used to diagnose, monitor and stratify patients with ileus.

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.

Progress in understanding of relationship between gut microbiota and gastrointestinal motility

Gastrointestinal motility disorders are a group of common clinical disorders in which abnormal gastrointestinal motility is the major pathogenesis, including irritable bowel syndrome, functional dyspepsia, and diabetic gastroparesis. With the rapid development of microbial sequencing technology in the past 10 years, the understanding of the gut microbiota has greatly improved, and it is generally found that patients with gastrointestinal motility diseases have gut microbiota disorders. Some progress has been made on the correlation between gut microbiota and gastrointestinal motility. This review aims to elucidate the relationship between gut microbiota and gastrointestinal motility and the mechanism of their interaction.

The Effect of Phenotype and Genotype on the Plasma Proteome in Patients with Inflammatory Bowel Disease

BACKGROUND AND AIMS

Protein profiling in patients with inflammatory bowel diseases [IBD] for diagnostic and therapeutic purposes is underexplored. This study analysed the association between phenotype, genotype, and the plasma proteome in IBD.

METHODS

A total of 92 inflammation-related proteins were quantified in plasma of 1028 patients with IBD (567 Crohn's disease [CD]; 461 ulcerative colitis [UC]) and 148 healthy individuals to assess protein-phenotype associations. Corresponding whole-exome sequencing and global screening array data of 919 patients with IBD were included to analyse the effect of genetics on protein levels (protein quantitative trait loci [pQTL] analysis). Intestinal mucosal RNA sequencing and faecal metagenomic data were used for complementary analyses.

RESULTS

Thirty-two proteins were differentially abundant between IBD and healthy individuals, of which 22 proteins were independent of active inflammation; 69 proteins were associated with 15 demographic and clinical factors. Fibroblast growth factor-19 levels were decreased in CD patients with ileal disease or a history of ileocecal resection. Thirteen novel cis-pQTLs were identified and 10 replicated from previous studies. One trans-pQTL of the fucosyltransferase 2 [FUT2] gene [rs602662] and two independent cis-pQTLs of C-C motif chemokine 25 [CCL25] affected plasma CCL25 levels. Intestinal gene expression data revealed an overlapping cis-expression [e]QTL-variant [rs3745387] of the CCL25 gene. The FUT2 rs602662 trans-pQTL was associated with reduced abundances of faecal butyrate-producing bacteria.

CONCLUSIONS

This study shows that genotype and multiple disease phenotypes strongly associate with the plasma inflammatory proteome in IBD, and identifies disease-associated pathways that may help to improve disease management in the future.

Male sex, ostomy, infection, and intravenous fluids are associated with increased risk of postoperative ileus in elective colorectal surgery

BACKGROUND

Postoperative ileus is a common and costly complication after elective colorectal surgery. Effects of intravenous fluid administration remain controversial, and the effect of ostomy construction has not been fully evaluated. Various restrictive intravenous fluid protocols may adversely affect renal function. We aimed to investigate the impact of intestinal reconstruction and intravenous fluid on ileus and renal function after colorectal resection under an enhanced recovery protocol.

METHODS

A retrospective study of a prospectively maintained institutional database for a tertiary academic medical center following National Surgical Quality Improvement Program standards was reviewed, analyzing elective colorectal resections performed under enhanced recovery protocol from 2015 to 2018. Postoperative ileus was defined as nasogastric decompression, nil per os >3 days postoperatively, or nasogastric tube insertion. Patients with and without ileus were compared. Intravenous fluid and different anastomoses and ostomies were investigated. Acute kidney injury was a secondary outcome, due to the potential of renal damage with restriction of intravenous fluid volume during and after surgery and controversy in current literature in this matter.

RESULTS

Postoperative ileus occurred in 18.5% of patients (n = 464). Male sex (odds ratio 1.97, 95% confidence interval 1.12-3.52) and postoperative infection (odds ratio 2.13, 95% confidence interval 1.03-4.35) were associated with ileus. Compared to colorectal anastomosis, ileostomy/ileorectal anastomosis had the highest risk of ileus (odds ratio 4.9, 95% confidence interval 2.33-11.3), colostomy second highest (odds ratio 3.3, 95% confidence interval 1.35-8.39), while ileocolic anastomosis did not significantly differ (odds ratio 2.06, 95% confidence interval 0.69-5.85) on multivariate analysis. Each liter of intravenous fluid within the first 72 hours significantly correlated with postoperative ileus (odds ratio 1.41, 95% confidence interval 1.27-1.59). Rates of acute kidney injury did not differ (P = .18).

CONCLUSION

Each additional liter of intravenous fluid given in the first 72 hours increased the risk of postoperative ileus 1.4-fold. There is substantially higher risk of ileus with male sex, infection, ileostomy/ileorectal anastomosis, and colostomy. Judicious use of intravenous fluid, as described in our enhanced recovery protocol, is not detrimental for renal function in the setting of normal baseline.

Effect of bowel preparation on intestinal permeability and inflammatory response during postoperative ileus in mice

BACKGROUND

Postoperative ileus entails pathophysiological changes in mucosal permeability and an intestinal inflammatory immune response. We hypothesized that preoperative selective decontamination of the digestive tract combined with preoperative mechanical bowel preparation might be advantageous to prevent or reduce permeability changes and immune response in postoperative ileus.

METHODS

Postoperative ileus was induced in mice by standardized small bowel manipulation. Intervention groups received selective decontamination and/or intestinal lavage with normal saline simulating mechanical bowel preparation before postoperative ileus induction. At 1, 3, and 9 hours after surgery, ileum samples were harvested for measurements of fluorescein (332 Da) permeability, quantification of tumor necrosis factor α-mRNA level, and leukocyte infiltration of the intestinal wall.

RESULTS

Mucosal fluorescein permeability increased at 1 hour (8.6 ± 1.1 vs 5.9 ± 0.9 10^-6 cm/s; P < .01) and 3 hours (8.5 ± 0.6 vs 6.5 ± 0.2 10^-6 cm/s; P < .05) after induction of postoperative ileus. This increase was prevented by mechanical bowel preparation and selective decontamination+mechanical bowel preparation interventions at both points in time. Expression of tumor necrosis factor α was more than 2-fold increased (P < .05) in the very early phase after induction of postoperative ileus but did not occur in mechanical bowel preparation-pretreated animals. Myeloperoxidase staining revealed that mechanical bowel preparation inhibited postoperative ileus-associated leukocyte infiltration of the intestinal muscularis at 3 and 9 hours after surgery, but not selective decontamination + mechanical bowel preparation treatment. The number of leukocytes after mechanical bowel preparation-only treatment remained at the level of sham-controls.

CONCLUSION

Mechanical bowel preparation prevents permeability and leukocyte infiltration of the intestinal wall in the early phase of postoperative ileus in mice.

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.

A Population of Radio-Resistant Macrophages in the Deep Myenteric Plexus Contributes to Postoperative Ileus Via Toll-Like Receptor 3 Signaling

Postoperative ileus (POI) is triggered by an innate immune response in the muscularis externa (ME) and is accompanied by bacterial translocation. Bacteria can trigger an innate immune response via toll-like receptor (TLR) activation, but the latter's contribution to POI has been disproved for several TLRs, including TLR2 and TLR4. Herein we investigated the role of double-stranded RNA detection via TLR3 and TIR-domain-containing adapter-inducing interferon-β (TRIF) signaling pathway in POI. POI was induced by small bowel intestinal manipulation in wt, TRIF^-/-, TLR3^-/-, type I interferon receptor^-/- and interferon-β reporter mice, all on C57BL/6 background, and POI severity was quantified by gene expression analysis, gastrointestinal transit and leukocyte extravasation into the ME. TRIF/TLR3 deficiency reduced postoperative ME inflammation and prevented POI. With bone marrow transplantation, RNA-sequencing, flow cytometry and immunohistochemistry we revealed a distinct TLR3-expressing radio-resistant MHCII^hiCX3CR1^- IBA-1⁺ resident macrophage population within the deep myenteric plexus. TLR3 deficiency in these cells, but not in MHCII^hiCX3CR1⁺ macrophages, reduced cytokine expression in POI. While this might not be an exclusive macrophage-privileged pathway, the TLR3/TRIF axis contributes to proinflammatory cytokine production in MHCII^hiCX3CR1^- IBA-1⁺ macrophages during POI. Deficiency in TLR3/TRIF protects mice from POI. These data suggest that TLR3 antagonism may prevent POI in humans.

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.

No Significant Effect of Daikenchuto (TJ-100) on Peritoneal IL-9 and IFN-γ Levels After Pancreaticoduodenectomy

Aim and Background

TJ-100 is a traditional Japanese medicine that affects inflammation and gastrointestinal motility, and is used as a preventive and treatment for paralytic ileus. This study aims at determining the effect of TJ-100 on the peritoneal levels of IFN-γ/IL-9, cytokines related to ileus, after pancreaticoduodenectomy (PD) in a clinical setting.

Methods

This was a subsidiary study of the clinical trial investigating the effect of TJ-100 on postoperative bowel function. Ascites was collected from 180 patients using an abdominal drainage tube on postoperative day 1 and 3 after PD (POD 1 or POD 3) and used to measure 27 cytokines. We performed univariate and multivariate analyses using several perioperative variables and administration of TJ-100/placebo to determine the effect of TJ-100 on the levels of IFN-γ and IL-9.

Results

Peritoneal levels of IL-9 and IFN-γ decreased between POD 1 and 3 (Wilcoxon signed-rank test p<0.001). Multivariate analysis was performed after univariate analysis to select the variables and patients with a body mass index of ≥22 kg/m², older age, use of epidural anesthesia, and longer surgery correlated with the levels of IL-9 and IFN-γ. However, we could not detect a correlation between the use of TJ-100 and cytokine levels in ascites either on POD 1 or 3.

Conclusion

TJ-100 did not affect peritoneal IL-9 and IFN-γ levels after PD. This was in accordance with published clinical findings showing no improvement in bowel function after PD and TJ-100 treatment.

Pretreatment with transcutaneous electrical acupoint stimulation to prevent postoperative ileus in patients undergoing laparoscopic colon surgery: study protocol for a randomised controlled trial

INTRODUCTION

Postoperative ileus (POI), a common complication after surgery, severely affects postoperative recovery. It is unclear whether pretreatment with transcutaneous electrical acupoint stimulation (TEAS) can improve recovery from POI. This trial will evaluate the effects of pretreatment with TEAS on POI.

METHODS AND ANALYSIS

This will be a prospective, randomised controlled trial. American Society of Anesthesiologists (ASA) physical status classification I-III level patients, aged 18-75 years and scheduled for laparoscopic colon surgery, will be included in the study. It is planned that 146 subjects will be randomised to the TEAS and sham TEAS (STEAS) groups. The groups will undergo two sessions of TEAS/STEAS daily for 3 days before surgery, with a final TEAS/STEAS treatment 30 min before anaesthesia. The primary endpoint of the study will be time to first defaecation. Secondary endpoints will include time to first flatus, time to tolerance of oral diet, GI-2 (composite outcome of time to first defaecation and time to tolerance of oral diet), time to independent walking, length of hospital stay, postoperative pain Visual Analogue Scale score on the first 3 days after surgery, analgesic requirements, complications and plasma concentrations of interferon-β (IFN-β), IFN-γ, interleukin-6 (IL-6) and IL-1β. Multiple linear regression will be used to identify independent predictors of outcome measures.

ETHICS AND DISSEMINATION

This study has been approved by the Chinese Registered Clinical Trial Ethics Review Committee (No. ChiECRCT-20170084). The results of the trial will be published in an international peer-reviewed journal.

TRIAL REGISTRATION NUMBER

This study has been registered with the Chinese Clinical Trial Registry (No. ChiCTR-INR-17013184).

TRIAL STATUS

The study was in the recruitment phase at the time of manuscript submission.

Intestinal resident macrophages: Multitaskers of the gut

BACKGROUND

Intestinal resident macrophages play a crucial role in homeostasis and have been implicated in numerous gastrointestinal diseases. While historically believed to be largely of hematopoietic origin, recent advances in fate-mapping technology have unveiled the existence of long-lived, self-maintaining populations located in specific niches throughout the gut wall. Furthermore, the advent of single-cell technology has enabled an unprecedented characterization of the functional specialization of tissue-resident macrophages throughout the gastrointestinal tract.

PURPOSE

The purpose of this review was to provide a panorama on intestinal resident macrophages, with particular focus to the recent advances in the field. Here, we discuss the functions and phenotype of intestinal resident macrophages and, where possible, the functional specialization of these cells in response to the niche they occupy. Furthermore, we will discuss their role in gastrointestinal diseases.

Effects of electroacupuncture on the intestinal motility and local inflammation are modulated by acupoint selection and stimulation frequency in postoperative ileus mice

BACKGROUND

Electroacupuncture (EA) is widely used in various gastrointestinal diseases around the world, including POI. Here, we investigated different therapeutic effects of EA using lower limb and abdomen acupoints.

METHODS

Intestinal manipulation was performed in 88 mice, and eight mice underwent a sham operation. Forty mice were randomly divided into model group and four EA groups receiving stimulation at ST36 (2, 10, 30, 100 Hz). The most effective frequency was then used in the following experiments. Forty-eight mice were randomly divided into six groups receiving EA treatment at ST37, ST39, ST25, CV4, CV12, and a non-acupuncture point. Gastrointestinal motility and plasma TNF-α, IL-6 were evaluated in all mice. The local immune response and α-smooth muscle actin (α-SMA) expression were assessed by immunofluorescence, ELISA, and HE staining.

RESULTS

ST36 stimulated with 10 or 30 Hz EA significantly increased the gastrointestinal motility and attenuated peripheral inflammation; however, ST36 stimulated with 2 or 100 Hz did not induce any effect. The therapeutic effects on motility and inflammation of 10 Hz EA in the ST36 group were similar in the ST36, ST37, ST39, or CV4 groups, but when applied to ST25, CV12 or non-acupoint had no significant differences. EA at ST36, ST37, ST39, or CV4 significantly inhibited local MPO activity, immune cells infiltration, and increased α-SMA.

CONCLUSIONS

EA at lower limb and abdomen acupoints with the same stimulation parameters had different therapeutic effects on postoperative dysmotility and inflammation. Furthermore, EA protected SMC to improve gastrointestinal transit by reducing local inflammation in the intestinal musculature in POI.

X-ray evaluation of intestinal dysmotility induced by Eimeria pragensis infection in C57BL/6 mice

This study was conducted to elucidate the intestinal dysmotility during coccidiosis. C57BL/6 male mice at seven weeks of age were inoculated with Eimeria pragensis sporulated oocysts (100 to 1,000 oocysts). The intestinal motility was evaluated by observing discharging time of barium sulfate (Ba₂SO₄) after oral administration (WITT: the whole intestinal transit time). The exact location of the dysmotility was analyzed by intermittent barium gastrography. Upper intestinal dysmotility was evaluated by charcoal propulsion study. Additionally, the occurrence of dysmotility was observed at different post-infection times (4, 7, and 14 days post-infection (d.p.i.)) and in infection-dose dependent manner (100, 300, and 1,000 oocysts). As the E. pragensis infected mice had significantly lower feed intake compared to the control group, we designed a feed apprehension study to evaluate the effect of low feed intake on the intestinal dysmotility. The WITT of infected mice at 7 d.p.i. was significantly longer (6 hr) than the uninfected mice (2.5 hr). Intestinal dysmotility was observed in the small intestine, caecum, and colorectum in the infected mice. Charcoal propulsion was slower in infected group (reaching to 40.4% of the whole small intestine) compared to control group (68.0%). The dysmotility was observed at the beginning of the patent period (7 d.p.i.) and subsided as the patency ended (14 d.p.i.). Mice with lower feed intake appeared to have similar intestinal motility as control mice. In summary, this study revealed the evidence of intestinal hypomotility during E. pragensis infection.

A comparative study about the immunomodulatory effects of tramadol and metamizole in a murine model of postoperative ileus

Postoperative ileus (POI) is a common complication after abdominal surgery characterized by motility disturbances leading to increased morbidity and mortality in surgical patients. Intestinal manipulation of the murine small bowel is an established animal model resulting in an increased postsurgical inflammation within the intestinal muscular externa and a delayed gastrointestinal transit. Some analgesics have been shown to affect inflammation. In this study, we compared the immunomodulatory effects of two different analgesics. Mice were treated with tramadol, metamizole or saline as a control in our established POI model. The postoperative inflammatory response was assessed by gene expression of pro-inflammatory cytokines at different time points and immunocytes extravasation into the muscularis externa. Functional motility analyses were performed by a gastrointestinal transit measurement. Metamizole application reduced the pro-inflammatory response after surgery and improved gastrointestinal motility, while tramadol showed no alteration in cytokine gene expression, influx of immunocytes and gastrointestinal transit compared with the controls. In conclusion. we suggest tramadol as analgesia in immunological studies on POI in mice as it does not affect the underlying inflammation of POI.

The H2S-Releasing Naproxen Derivative ATB-346 and the Slow-Release H2S Donor GYY4137 Reduce Intestinal Inflammation and Restore Transit in Postoperative Ileus

Objective: Intestinal inflammation triggers postoperative ileus (POI), commonly seen after abdominal surgery and characterized by impaired gastrointestinal transit; when prolonged, this leads to increased morbidity. Hydrogen sulfide (H2S) is recognized as an important mediator of many (patho)physiological processes, including inflammation, and is now investigated for anti-inflammatory application. Therefore, the aim of this study was to investigate the effect of the H2S-releasing naproxen derivative ATB-346, developed to reduce gastrointestinal injury by naproxen, and the slow-release H2S donor GYY4137 on intestinal inflammation and delayed gastrointestinal transit in murine POI. Methods: C57Bl6J mice were fasted for 6 h, anesthetized and after laparotomy, POI was induced by compressing the small intestine with two cotton applicators for 5 min (intestinal manipulation; IM). GYY4137 (50 mg/kg, intraperitoneally), ATB-346 (16 mg/kg, intragastrically) or naproxen (10 mg/kg, intragastrically) were administered 1 h before IM. At 24 h postoperatively, gastrointestinal transit was assessed via fluorescent imaging, and mucosa-free muscularis segments were prepared for later analysis. Inflammatory parameters and activity of inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2 were measured. Histological examination of whole tissue sections was done on hematoxylin-eosin stained slides. Results: Pre-treatment with GYY4137 (geometric center; GC: 7.6 ± 0.5) and ATB-346 (GC: 8.4 ± 0.3) prevented the delayed transit induced by IM (GC: 3.6 ± 0.5 vs. 9.0 ± 0.4 in non-operated controls) while naproxen only partially did (GC: 5.9 ± 0.5; n = 8 for all groups). GYY4137 and ATB-346 significantly reduced the IM-induced increase in muscular myeloperoxidase (MPO) activity and protein levels of interleukin (IL)-6, IL-1β and monocyte chemotactic protein 1; the reduction by naproxen was less pronounced and only reached significance for MPO activity and IL-6 levels. All treatments significantly reduced the increase in COX-2 activity caused by IM, whereas only GYY4137 significantly reduced the increase in iNOS activity. Naproxen treatment caused significant histological damage of intestinal villi. Conclusion: The study shows that naproxen partially prevents POI, probably through its inhibitory effect on COX-2 activity. Both ATB-346 and GYY4137 were more effective, the result with GYY4137 showing that H2S per se can prevent POI.

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.

Identifying Therapeutic Targets for Sepsis Research: A Characterization Study of the Inflammatory Players in the Cecal Ligation and Puncture Model

During sepsis, disturbed gastrointestinal motility and increased mucosal permeability can aggravate sepsis due to the increased risk of bacterial translocation. To help identify new therapeutic targets, there is a need for animal models that mimic the immunological changes in the gastrointestinal tract as observed during human sepsis. We therefore characterized in detail the gastrointestinal neuroimmune environment in the cecal ligation and puncture (CLP) model, which is the gold standard animal model of microbial sepsis. Mice were sacrificed at day 2 and day 7, during which gastrointestinal motility was assessed and cytokines were measured in the serum and the colon. In the spleen, lymph nodes, ileum, and colon, subsets of leukocyte populations were identified by flow cytometry. Septic animals displayed an impaired gastrointestinal motility at day 2 and day 7. Two days post-CLP, increased serum and colonic levels of proinflammatory cytokines were measured. Flow cytometry revealed an influx of neutrophils in the colon and ileum, increased numbers of macrophages in the spleen and mesenteric lymph nodes, and an enhanced number of mast cells in all tissues. At day 7 post-CLP, lymphocyte depletion was observed in all tissues coinciding with increased IL-10 and TGF-β levels, as well as increased colonic levels of IL-17A and IFN-γ. Thus, CLP-induced sepsis in mice results in simultaneous activation of pro- and anti-inflammatory players at day 2 and day 7 in different tissues, mimicking human sepsis.

Role of transient receptor potential melastatin 2 in surgical inflammation and dysmotility in a mouse model of postoperative ileus

In this study, we investigated the role of transient receptor potential melastatin 2 (TRPM2), a nonselective cation channel abundantly expressed in inflammatory cells such as macrophages, in the development of postoperative ileus, a complication of abdominal surgery characterized by gastrointestinal dysmotility. In wild-type mice, we found that intestinal manipulation, a maneuver that elicits symptoms typical of postoperative ileus, delays the transit of fluorescein-labeled dextran, promotes the infiltration of CD68⁺ macrophages, Ly6B.2⁺ neutrophils, and MPO⁺ cells into intestinal muscles, boosts expression of IL-1β, IL-6, TNF-α, iNOS, and CXCL2 in intestinal muscles and peritoneal macrophages, enhances phosphorylation of ERK and p38 MAPK in intestinal muscles, and amplifies IL-1β, IL-6, TNF-α, iNOS, and CXCL2 expression in resident and thioglycolate-elicited peritoneal macrophages following exposure to lipopolysaccharide. Remarkably, TRPM2 deficiency completely blocks or diminishes these effects. Indeed, intestinal manipulation appears to activate TRPM2 in resident muscularis macrophages and elicits release of inflammatory cytokines and chemokines, which, in turn, promote infiltration of macrophages and neutrophils into the muscle, ultimately resulting in dysmotility. NEW & NOTEWORTHY Activation of transient receptor potential melastatin 2 (TRPM2) releases inflammatory cytokines and chemokines, which, in turn, promote the infiltration of inflammatory cells and macrophages into intestinal muscles, ultimately resulting in dysmotility. Thus TRPM2 is a promising target in treating dysmotility due to postoperative ileus, a complication of abdominal surgery.

Alterations in the gut barrier and involvement of Toll-like receptor 4 in murine postoperative ileus

BACKGROUND

The changes in the gut barrier (GB) and associated mechanisms in postoperative ileus (POI) are still unclear. Toll-like receptor 4 (TLR4) is involved in inflammation, which may cause GB dysfunction and POI. Here, the roles of the GB in POI in relation to TLR4-dependent signaling pathways were explored.

METHODS

POI was induced by small bowel manipulation in wild-type (WT) and TLR4-knockout (TLR4-/-) mice. Twenty-four hours after manipulation, indices of gastrointestinal (GI) transit, GB structure and function, inflammation, and related signaling pathways were analyzed.

KEY RESULTS

Normal GI motility and GB function were not affected by TLR4 knockout. Compared with WT POI mice, TLR4-/-POI mice showed milder GI transit retardation, GB dysfunction, and inflammatory responses. In WT mice, GB disorder was characterized by colonic goblet cells depletion, increased gut claudin-2 expression, and decreased CD4+/CD8+ ratios in intestinal Peyer's patches. Green fluorescent protein-tagged Escherichia coli in the gut was detected in plasma and extraintestinal organs, followed with increased plasma lipopolysaccharide. These changes displayed in WT POI mice were less severe in TLR4-/-POI mice. Furthermore, the mRNA and protein expression of interleukin-6, monocyte chemotactic protein-1, pp38 and pJNK in the intestine, and TNF-α level in plasma were significantly increased in WT, but not TLR4-/-POI mice.

CONCLUSIONS & INFERENCES

These results indicate that GB is impaired in the experimental POI, with inflammation being involved in this pathological process. TLR4 deficiency alleviated GB dysfunction and suppressed inflammation by disrupting the activation of mitogen-activated protein kinase signaling pathways, thereby ameliorating POI.

Irf4-dependent CD103+CD11b+ dendritic cells and the intestinal microbiome regulate monocyte and macrophage activation and intestinal peristalsis in postoperative ileus

OBJECTIVE

Postoperative ileus (POI), the most frequent complication after intestinal surgery, depends on dendritic cells (DCs) and macrophages. Here, we have investigated the mechanism that activates these cells and the contribution of the intestinal microbiota for POI induction.

DESIGN

POI was induced by manipulating the intestine of mice, which selectively lack DCs, monocytes or macrophages. The disease severity in the small and large intestine was analysed by determining the distribution of orally applied fluorescein isothiocyanate-dextran and by measuring the excretion time of a retrogradely inserted glass ball. The impact of the microbiota on intestinal peristalsis was evaluated after oral antibiotic treatment.

RESULTS

We found that Cd11c-Cre⁺ Irf4^flox/flox mice lack CD103⁺CD11b⁺ DCs, a DC subset unique to the intestine whose function is poorly understood. Their absence in the intestinal muscularis reduced pathogenic inducible nitric oxide synthase (iNOS) production by monocytes and macrophages and ameliorated POI. Pathogenic iNOS was produced in the jejunum by resident Ly6C^- macrophages and infiltrating chemokine receptor 2-dependent Ly6C⁺ monocytes, but in the colon only by the latter demonstrating differential tolerance mechanisms along the intestinal tract. Consistently, depletion of both cell subsets reduced small intestinal POI, whereas the depletion of Ly6C⁺ monocytes alone was sufficient to prevent large intestinal POI. The differential role of monocytes and macrophages in small and large intestinal POI suggested a potential role of the intestinal microbiota. Indeed, antibiotic treatment reduced iNOS levels and ameliorated POI.

CONCLUSIONS

Our findings reveal that CD103⁺CD11b⁺ DCs and the intestinal microbiome are a prerequisite for the activation of intestinal monocytes and macrophages and for dysregulating intestinal motility in POI.

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.

Intestinal T lymphocyte homing is associated with gastric emptying and epithelial barrier function in critically ill: a prospective observational study

Background

Impaired gastric emptying is common in critically ill patients. Intestinal dysmotility, a major cause of feed intolerance, may foster infectious complications due to mucosal barrier disruption. However, little is known about gut-directed immune activation, intestinal barrier function and its association with impaired gastric emptying in critically ill patients at ICU admission.

Methods

We conducted a prospective observational study at two tertiary care medical ICUs. Fifty consecutive patients needing invasive mechanical ventilation were recruited within 24 h of ICU admission, prior to any nutritional support. The acute physiology and chronic health evaluation (APACHE) II score, the sequential organ failure assessment (SOFA) score and the multiple organ dysfunction score (MODS) were used to assess illness severity and multiple organ dysfunction. Gastric emptying was assessed by paracetamol absorption test. Peripheral blood mononuclear cells were freshly isolated and cultured for 24 h, and TNF-α, IL-1β and IL-10 measured in cell culture supernatants and in serum by ELISA. The intestinal epithelial barrier was assessed, quantifying serum concentrations of intestinal fatty acid binding protein (I-FABP), ileal bile-acid binding protein (I-BABP) and zonulin-1 by ELISA. Small bowel homing T lymphocytes (CD4+ α4β7 + CCR9+) were analyzed by flow cytometry. The Mann-Whitney test and Spearman correlation were used in statistical evaluation.

Results

CD4 + α4β7 + CCR9+ T lymphocytes were inversely correlated with gastric emptying. Patients with delayed gastric emptying at ICU admission (n = 35) had significantly higher serum and PBMC-induced TNF-α and IL-1β and increased intestinal barrier disruption reflected by higher I-FABP, I-BABP and zonulin-1. Patients who died in the ICU had significantly impaired gastric empting at admission compared to ICU survivors. No differences were observed in APACHE II, SOFA or MODS in patients with delayed gastric emptying compared to patients with normal gastric emptying.

Conclusions

Exaggerated CD4 + α4β7 + CCR9+ T lymphocyte homing with increased pro-inflammatory cytokine release and intestinal epithelial barrier disruption are associated with delayed gastric emptying. This is not simply due to differences in overall severity of illness at ICU admission and may represent a pathophysiological mechanism of gut-directed immune activation leading to impaired barrier function in the critically ill.

Resident macrophages in the healthy and inflamed intestinal muscularis externa

Macrophages reside in a dense cellular network in the intestinal muscularis externa, and there is emerging evidence that the functionality of these cells determines the local microenvironment. Inflammatory responses during intestinal diseases change the homeostatic functionality of these cells causing inflammation and intestinal dysmotility. Such disturbances are not only induced by a change in the cellular composition in the intestinal muscularis but also by an altered crosstalk with the peripheral and central nervous system. In this review, we summarize the role of muscularis macrophages in the intestine in homeostasis and inflammation. We compare the functionality, the phenotype, and the origin of muscularis macrophages to their neighboring counterparts within the different layers of the intestine. We outline the cellular crosstalk with the enteric and the peripheral nervous system and summarize the current therapeutic approaches to modulate the functionality of these phagocytes.

Electroacupuncture treatment partly promotes the recovery time of postoperative ileus by activating the vagus nerve but not regulating local inflammation

Postoperative ileus (POI) after abdominal surgery significantly lowers the life quality of patients and increase hospital costs. However, few treatment strategies have successfully shortened the duration of POI. Electroacupuncture (EA) is a modern way of administering acupuncture and widely used in various gastrointestinal (GI) diseases in the world. Here, we studied the effect of EA on POI and its underlying mechanisms. Intestinal manipulation resulted in significant delays of GI transit, colonic transit and gastric emptying. Surgery also up-regulated c-fos in nucleus of the solitary tract (NTS) and induced inflammation response in the small intestine. Further, operation and inhale anesthesia inhibited NTS neuron excitation duration for the whole observation time. EA administered at ST36 indeed shortened the recovery time of GI and colonic transit, and significantly increased the gastric emptying. EA also significantly activated the NTS neurons after operation. However, there was no anti-inflammation effect of EA during the whole experiment. Finally, atropine blocked the regulatory effect of EA on GI function, when it was injected after surgery, but not before surgery. Thus, the regulatory effect of EA on POI was mainly mediated by exciting NTS neurons to improve the GI tract transit function but not by activating cholinergic anti-inflammatory pathway.

Randomized Clinical Trial Comparing Efficacy of Simo Decoction and Acupuncture or Chewing Gum Alone on Postoperative Ileus in Patients With Hepatocellular Carcinoma After Hepatectomy

To compare the efficacy of simo decoction (SMD) combined with acupuncture at the tsusanli acupoint or chewing gum alone for treating postoperative ileus in patients with hepatocellular carcinoma (HCC) after hepatectomy.In postoperative ileus, a frequent complication following hepatectomy, bowel function recovery is delayed, which increases length of hospital stay. Studies suggest that chewing gum may reduce postoperative ileus; SMD and acupuncture at the tsusanli acupoint have long been used in China to promote bowel movement.Patients with primary HCC undergoing hepatectomy between January 2015 and August 2015 were randomized to receive SMD and acupuncture (n = 55) or chewing gum (n = 53) or no intervention (n = 54) starting on postoperative day 1 and continuing for 6 consecutive days or until flatus. Primary endpoints were occurrence of postoperative ileus and length of hospital stay; secondary endpoints were surgical complications.Groups treated with SMD and acupuncture or with chewing gum experienced significantly shorter time to first peristalsis, flatus, and defecation than the no-intervention group (all P < 0.05). Hospital stay was significantly shorter in the combined SMD and acupuncture group (mean 14.0 d, SD 4.9) than in the no-intervention group (mean 16.5 d, SD 6.8; P = 0.014), while length of stay was similar between the chewing gum group (mean 14.7, SD 6.2) and the no-intervention group (P = 0.147). Incidence of grades I and II complications was slightly lower in both intervention groups than in the no-intervention group.The combination of SMD and acupuncture may reduce incidence of postoperative ileus and shorten hospital stay in HCC patients after hepatectomy. Chewing gum may also reduce incidence of ileus but does not appear to affect hospital stay. (Clinicaltrials.gov registration number: NCT02438436.).

Establishing a biomarker for postoperative ileus in humans - Results of the BiPOI trial

AIMS

Postoperative ileus (POI) is a frequent complication after abdominal surgery, resulting from an inflammation of the muscularis externa (ME). So far no valid biomarker for occurrence, duration or intensity of POI exists. Extravasation of monocytes and neutrophils from blood circulating into the postoperative ME is well known as a hallmark of POI. In a previous study we demonstrated that a low abundant subset of TH1 cells, activated by IL-12, can be detected in the peripheral blood of a small subset of patients in response to abdominal surgery. The aim of the present study was to investigate if these specific TH1 cells, IL-12 or circulating leukocyte levels could act as a valid marker for POI occurrence.

MAIN METHODS

At different time points, blood samples of patients undergoing abdominal or extraabdominal surgery were collected. Serum levels of IL-12 or TH1 cells as well as neutrophils and monocytes were analyzed. Data were compared between both groups and correlated with clinical signs of POI.

KEY FINDINGS

Time until first flatus and defecation as well as solid food tolerances are delayed after abdominal compared to extraabdominal surgery. Circulating IL-12 levels and numbers of TH1 cells, neutrophils and monocytes did not differ between both groups.

SIGNIFICANCE

While previous experiments indicated that specific TH1 cells play a crucial role in POI dissemination, our present data from a larger human cohort demonstrate that they do not seem to be suitable to distinguish between abdominal and extraabdominal surgery. Furthermore neither TH1 cells nor leukocytes or serum IL-12 levels are appropriate biomarkers for POI in a clinical setting.

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.

The contribution of mast cells to postoperative ileus in experimental and clinical studies

The persistent phase of postoperative ileus (POI) is mediated by inflammatory activation of the resident myeloid immune cell population in the gut wall, likely elicited by neurogenic activation. Mast cells are thought to play a critical role in this inflammatory response and involvement of mast cells in POI has been investigated and described thoroughly in experimental studies. Intestinal manipulation (IM) leads to degranulation of mast cells, resulting in an increase in mast cell proteases in peritoneal fluid and gut tissue. The inflammatory infiltrate formed in the intestinal wall thereby impairs gastrointestinal motility. In the clinical study by Berdun et al., the experimentally known association between mast cell degranulation and delayed motility is shown in a clinical setting. These findings are important and open up therapeutic opportunities to reduce or prevent POI. In this mini-review, the role of mast cells in POI is discussed. Furthermore, an update is given on the involvement of the inflammatory response in POI and potential therapeutic strategies.

CCR9 antagonism: potential in the treatment of Inflammatory Bowel Disease

Inflammatory Bowel Disease (IBD), mainly comprising Crohn’s disease (CD) and ulcerative colitis (UC), is a chronic condition that primarily affects the intestine and is characterized by leukocytic infiltration. Blocking the migration of leukocytes from the circulation is therefore a reasonable therapeutic goal. Recent clinical trials using this approach have shown promise, with the monoclonal antibody to α₄β₇ integrin, vedolizumab, and previously with the monoclonal antibody to the α₄ subunit, natalizumab. Directly targeting the subset of α₄β₇ expressing cells that co-express CC chemokine receptor 9 (CCR9), using the orally administered antagonist, CCX282-B, also known as vercirnon, has also been evaluated in Phase II and III trials that have produced mixed results. Although CCX282-B showed efficacy in inducing response in active CD in early studies, this was not confirmed in a Phase III study. CCX282-B was also more effective than placebo in maintaining remission, and this result has yet to be confirmed in Phase III. The efficacy of blocking CCR9 in UC, where vedolizumab was effective, has not been tested. The prospect of targeting CCR9 in IBD remains attractive. Much of the local accumulation of inflammatory cells in the intestine arises from migration rather than local proliferation and genetic and pharmacological targeting of CCR9 or its ligand in preclinical models that mimic UC and CD ameliorate inflammation in some cases. Furthermore, binding of chemokine ligands to receptor is a critical step in activating integrin binding, so there is a potential for synergistic action between integrin and chemokine antagonists. CCR9 is expressed on a smaller proportion of circulating cells than α₄β₇ integrin, which may offer greater specificity of effect, particularly in long term use. Furthermore, while α₄β₇ is widely expressed on T and B cell subsets, CCR9 is mainly expressed on effector memory Th1 cells. Indications for the use of intestine-specific integrin and chemokine receptor targeting may also extend beyond IBD, to include, for example, postoperative ileus, and primary sclerosing cholangitis.

Commensal bacterial internalization by epithelial cells: An alternative portal for gut leakiness

Co-existing paracellular and transcellular barrier defect in intestinal epithelium was documented in inflammatory bowel disease, celiac disease, and intestinal obstruction. Mechanisms regarding tight junction disruption have been extensively studied; however, limited progress has been made in research on bacterial transcytosis. Densely packed brush border (BB), with cholesterol-based lipid rafts in the intermicrovillous membrane invagination, serves as an ultrastructural barrier to prevent direct contact of luminal microbes with the cellular soma. Evidence in in vitro epithelial cell cultures and in vivo animal models of bowel obstruction and antibiotic-resistant bacterial infection had indicated that nonpathogenic, noninvasive enteric bacteria may hijack the lipid raft-mediated endocytic pathways. Our studies have shown that low dose interferon-gamma (IFNγ) causes long myosin light chain kinase (MLCK)-dependent terminal web (TW) contraction and BB fanning, allowing bacteria to pass through the consequently widened intermicrovillous cleft to be endocytosed via caveolin-associated lipid rafts. Activation of intracellular innate immune receptors by bacteria-containing endosomes may further induce inflammatory and oxidative stress, leading to secondary tight junction damage. The finding of bacterial internalization preceding tight junction damage suggests that abnormal bacterial uptake by epithelial cells may contribute to the initiation or relapse of chronic intestinal inflammation.

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

BACKGROUND AND PURPOSE

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

EXPERIMENTAL APPROACH

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

KEY RESULTS

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

CONCLUSION AND IMPLICATIONS

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

Randomized clinical trial of the effect of gum chewing on postoperative ileus and inflammation in colorectal surgery

BACKGROUND

Postoperative ileus (POI) is a common complication following colorectal surgery that delays recovery and increases length of hospital stay. Gum chewing may reduce POI and therefore enhance recovery after surgery. The aim of the study was to evaluate the effect of gum chewing on POI, length of hospital stay and inflammatory parameters.

METHODS

Patients undergoing elective colorectal surgery in one of two centres were randomized to either chewing gum or a dermal patch (control). Chewing gum was started before surgery and stopped when oral intake was resumed. Primary endpoints were POI and length of stay. Secondary endpoints were systemic and local inflammation, and surgical complications. Gastric emptying was measured by ultrasonography. Soluble tumour necrosis factor receptor 1 (TNFRSF1A) and interleukin (IL) 8 levels were measured by enzyme-linked immunosorbent assay.

RESULTS

Between May 2009 and September 2012, 120 patients were randomized to chewing gum (58) or dermal patch (control group; 62). Mean(s.d.) length of hospital stay was shorter in the chewing gum group than in controls, but this difference was not significant: 9·5(4·9) versus 14·0(14·5) days respectively. Some 14 (27 per cent) of 52 analysed patients allocated to chewing gum developed POI compared with 29 (48 per cent) of 60 patients in the control group (P = 0·020). More patients in the chewing gum group first defaecated within 4 days of surgery (85 versus 57 per cent; P = 0·006) and passed first flatus within 48 h (65 versus 50 per cent; P = 0·044). The decrease in antral area measured by ultrasonography following a standard meal was significantly greater among patients who chewed gum: median 25 (range -36 to 54) per cent compared with 10 (range -152 to 54) per cent in controls (P = 0·004). Levels of IL-8 (133 versus 288 pg/ml; P = 0·045) and TNFRSF1A (0·74 versus 0·92 ng/ml; P = 0·043) were lower among patients in the chewing gum group. Fewer patients in this group developed a grade IIIb complication (2 of 58 versus 10 of 62; P = 0·031).

CONCLUSION

Gum chewing is a safe and simple treatment to reduce POI, and is associated with a reduction in systemic inflammatory markers and complications.

REGISTRATION NUMBER

NTR2867 (http://www.trialregister.nl).