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

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.

Gut microbiota as a key regulator of intestinal mucosal immunity

Gut microbiota is a complex microbial community with the ability of maintaining intestinal health. Intestinal homeostasis largely depends on the mucosal immune system to defense external pathogens and promote tissue repair. In recent years, growing evidence revealed the importance of gut microbiota in shaping intestinal mucosal immunity. Therefore, according to the existing findings, this review first provided an overview of intestinal mucosal immune system before summarizing the regulatory roles of gut microbiota in intestinal innate and adaptive immunity. Specifically, this review delved into the gut microbial interactions with the cells such as intestinal epithelial cells (IECs), macrophages, dendritic cells (DCs), neutrophils, and innate lymphoid cells (ILCs) in innate immunity, and T and B lymphocytes in adaptive immunity. Furthermore, this review discussed the main effects of gut microbiota dysbiosis in intestinal diseases and offered future research prospects. The review highlighted the key regulatory roles of gut microbiota in intestinal mucosal immunity via various host-microbe interactions, providing valuable references for the development of microbial therapy in intestinal diseases.

Origin and Function of Monocytes in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a chronic disease resulting from the interaction of various factors such as social elements, autoimmunity, genetics, and gut microbiota. Alarmingly, recent epidemiological data points to a surging incidence of IBD, underscoring an urgent imperative: to delineate the intricate mechanisms driving its onset. Such insights are paramount, not only for enhancing our comprehension of IBD pathogenesis but also for refining diagnostic and therapeutic paradigms. Monocytes, significant immune cells derived from the bone marrow, serve as precursors to macrophages (Mφs) and dendritic cells (DCs) in the inflammatory response of IBD. Within the IBD milieu, their role is twofold. On the one hand, monocytes are instrumental in precipitating the disease's progression. On the other hand, their differentiated offsprings, namely moMφs and moDCs, are conspicuously mobilized at inflammatory foci, manifesting either pro-inflammatory or anti-inflammatory actions. The phenotypic spectrum of these effector cells, intriguingly, is modulated by variables such as host genetics and the subtleties of the prevailing inflammatory microenvironment. Notwithstanding their significance, a palpable dearth exists in the literature concerning the roles and mechanisms of monocytes in IBD pathogenesis. This review endeavors to bridge this knowledge gap. It offers an exhaustive exploration of monocytes' origin, their developmental trajectory, and their differentiation dynamics during IBD. Furthermore, it delves into the functional ramifications of monocytes and their differentiated progenies throughout IBD's course. Through this lens, we aspire to furnish novel perspectives into IBD's etiology and potential therapeutic strategies.

Electroacupuncture alleviates intestinal inflammation via a distinct neuro-immune signal pathway in the treatment of postoperative ileus

BACKGROUND

The induction of intestinal inflammation as a result of abdominal surgery is an essential factor in postoperative ileus (POI) development. Electroacupuncture (EA) at ST36 has been demonstrated to relieve intestinal inflammation and restore gastrointestinal dysmotility in POI. This study aims to elucidate the neuroimmune pathway involved in the anti-inflammatory properties of EA in POI.

METHODS

After intestinal manipulation (IM) was performed to induce POI, intestinal inflammation and motility were assessed 24 h post-IM, by evaluating gastrointestinal transit (GIT), cytokines expression, and leukocyte infiltration. Experimental surgery, pharmacological intervention, and genetic knockout mice were used to elucidate the neuroimmune mechanisms of EA.

RESULTS

EA at ST36 significantly improved GIT and reduced the expression of pro-inflammatory cytokines and leukocyte infiltration in the intestinal muscularis following IM in mice. The anti-inflammatory effectiveness of EA treatment was abolished by sub-diaphragmatic vagotomy, whereas splenectomy did not hinder the anti-inflammatory benefits of EA treatment. The hexamethonium chloride (HEX) administration contributes to a notable reduction in the EA capacity to suppress inflammation and enhance motility dysfunction, and EA is ineffective in α7 nicotinic acetylcholine receptor (α7nAChR) knockout mice.

CONCLUSIONS

EA at ST36 prevents intestinal inflammation and dysmotility through a neural circuit that requires vagal innervation but is independent of the spleen. Further findings revealed that the process involves enteric neurons mediating the vagal signal and requires the presence of α7nAChR. These findings suggest that utilizing EA at ST36 may represent a possible therapeutic approach for POI and other immune-related gastrointestinal diseases.

Laparoscopic versus open surgery in obstructive colorectal cancer patients following stents placement: a comprehensive meta-analysis of cohort studies

BACKGROUND

Over the past decade, the use of stent placement as a bridge to surgery (BTS) has emerged as an alternative to emergency surgery for patients with (OCRC). However, the optimal surgical approach remains indeterminate. This study seeks to evaluate the safety and feasibility of a combined treatment modality involving stent placement and laparoscopic surgery for OCRC presenting with malignant obstruction.

METHODS

A comprehensive search of PubMed, Cochrane Library, EMBASE, Web of Science, and ClinicalTrials.gov was conducted until June 2023 to identify studies that compared laparoscopic to open surgery in patients with OCBC following stent insertion.

RESULTS

The meta-analysis incorporated 12 cohort studies, encompassing 933 patients. There was no statistically significant difference in the 30-day mortality rates between the two groups (relative risk [RR], 1.09; 95% confidence interval [CI] 0.26 to 4.48; P = 0.95). Compared to the laparoscopic approach group, the open approach group had a higher rate of overall postoperative complications (POCs) (RR 0.52; 95% CI 0.37 to 0.72, P < 0.0001). There was no significant variance in lymph node (LN) dissection number between the groups (mean differences [MD], 1.64; 95% CI - 1.51 to 4.78; P = 0.31). Notably, laparoscopic surgery resulted in less intraoperative blood loss (MD, - 25.84 ml; 95% CI - 52.16 to 0.49; P = 0.05) and a longer operation time (MD, 20.99 mins; 95% CI 2.31 to 39.44; P = 0.03). The laparoscopic approach was associated with a shorter length of hospital stay (LOS) (MD - 3.29 days; 95% CI - 5.27 to 1.31; P = 0.001). Conversely, the open approach group had a higher rate of postoperative surgical site infection (SSI) (RR 0.47; 95% CI 0.23 to 0.96, P = 0.04). Although the number of included studies was insufficient to conduct a meta-analysis, several of them imply that laparoscopic surgery may yield more favorable outcomes in terms of the 3-year overall survival rate (OS), 3-year disease-free survival rate (DFS), 5-year OS, and 5-year DFS when compared to open surgery. It is worth noting that these differences lack statistical significance.

CONCLUSION

In patients with OCRC subjected to stent insertion, laparoscopic surgery arguably presents a modest superiority over open surgery by diminishing the overall postoperative risk and potentially reducing the LOS.

Emerging roles of MITF as a crucial regulator of immunity

Microphthalmia-associated transcription factor (MITF), a basic helix-loop-helix leucine zipper transcription factor (bHLH-Zip), has been identified as a melanocyte-specific transcription factor and plays a critical role in melanocyte survival, differentiation, function, proliferation and pigmentation. Although numerous studies have explained the roles of MITF in melanocytes and in melanoma development, the function of MITF in the hematopoietic or immune system-beyond its function in melanin-producing cells-is not yet fully understood. However, there is convincing and increasing evidence suggesting that MITF may play multiple important roles in immune-related cells. Therefore, this review is focused on recent advances in elucidating novel functions of MITF in cancer progression and immune responses to cancer. In particular, we highlight the role of MITF as a central modulator in the regulation of immune responses, as elucidated in recent studies.

Fecal microbiota transplantation regulates the microbiota-gut-spinal cord axis to promote recovery after spinal cord injury

Spinal cord injury (SCI) is devastating for patients, and currently lacks effective treatments. Dysbiosis commonly occurs after SCI and has significant immunomodulatory effects, but its impact on recovery remains unclear. The current study investigated the effects and mechanisms of fecal microbiota transplantation (FMT) in SCI. FMT was administered in a rat model of SCI and spinal pathology, inflammatory cytokines, and gut microbiome composition were assessed. Flow cytometry identified a source of interleukin (IL)-17 in spinal cord tissues, and carboxyfluorescein succimidyl ester labeling tracked γδ T cell migration. In vitro coculture was used to analyze the regulatory mechanisms of γδ T cells. Seahorse analysis was used to profile dendritic cell (DC) metabolism. Here we show that FMT improved spinal pathology and dampened post-injury inflammation. It also corrected post-SCI dysbiosis, increasing levels of the beneficial bacterium Akkermansia. The therapeutic effects of FMT were mediated by IL-17 produced by γδ T cells. FMT regulated γδ T cells via DC-T regulatory cell interaction, and induced metabolic reprogramming in DCs. These findings suggest that FMT represents a promising therapeutic approach for SCI, with potential to target IL-17+ γδ T cells. Elucidating the interconnected pathways between microbiota, immunity, and the spinal cord may facilitate novel treatment strategies.

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.

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

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

Conventional type 1 dendritic cells protect against gut barrier disruption via maintaining Akkermansia muciniphila in alcoholic steatohepatitis

BACKGROUND AND AIMS

Alcohol-perturbed gut immune homeostasis is associated with the development of alcoholic liver disease (ALD). However, the role of intestinal dendritic cells (DCs) in ALD progression is still unknown. This study aimed to investigate the cellular and molecular mechanisms through which intestinal DCs respond to alcohol exposure and contribute to the pathogenesis of ALD.

APPROACH AND RESULTS

After 8 weeks of alcohol consumption, the number of basic leucine zipper transcription factor ATF-like 3 ( Batf3 )-dependent conventional type 1 DCs (cDC1s) was dramatically decreased in the intestine but not the liver. cDC1 deficient Batf3 knockout mice along with wild-type mice were subjected to chronic-binge ethanol feeding to determine the role of intestinal cDC1s reduction in ALD. cDC1s deficiency exacerbated alcohol-induced gut barrier disruption, bacterial endotoxin translocation into the circulation, and liver injury. Adoptive transfer of cDC1s to alcohol-fed mice ameliorated alcohol-mediated gut barrier dysfunction and liver injury. Further studies revealed that intestinal cDC1s serve as a positive regulator of Akkermansia muciniphila ( A. muciniphila ). Oral administration of A. muciniphila markedly reversed alcoholic steatohepatitis in mice. Mechanistic studies revealed that cDC1s depletion exacerbated alcohol-downregulated intestinal antimicrobial peptides which play a crucial role in maintaining A. muciniphila abundance, by disrupting the IL-12-interferon gamma signaling pathway. Lastly, we identified that intestinal cDC1s were required for the protective role of Lactobacillus reuteri in alcoholic steatohepatitis.

CONCLUSIONS

This study demonstrated that cDC1s protect alcohol-induced liver injury by maintaining A. muciniphila abundance in mice. Targeting cDC1s may serve as a promising therapeutic approach for treating ALD.

Alterations of gut microbiome following gastrointestinal surgical procedures and their potential complications

Intestinal microorganisms play a crucial role in shaping the host immunity and maintaining homeostasis. Nevertheless, alterations in gut bacterial composition may occur and these alterations have been linked with the pathogenesis of several diseases. In surgical practice, studies revealed that the microbiome of patients undergoing surgery changes and several post-operative complications seem to be associated with the gut microbiota composition. In this review, we aim to provide an overview of gut microbiota (GM) in surgical disease. We refer to several studies which describe alterations of GM in patients undergoing different types of surgery, we focus on the impacts of peri-operative interventions on GM and the role of GM in development of post-operative complications, such as anastomotic leak. The review aims to enhance comprehension regarding the correlation between GM and surgical procedures based in the current knowledge. However, preoperative and postoperative synthesis of GM needs to be further examined in future studies, so that GM-targeted measures could be assessed and the different surgery complications could be reduced.

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.

The Role of Probiotics in Inflammation Associated with Major Surgery: A Narrative Review

Background: Gut microbiota is well-known for its ability to maintain intestinal homeostasis. However, the disruption of this homeostasis, known as dysbiosis, leads to multiple consequences, including local and systemic inflammation. Surgery-induced inflammation is a major concern for patients, as it leads to many infectious and non-infectious complications. Objective: The purpose of this review was to explore the role of probiotics and symbiotics in surgery-induced inflammation and to determine if their use is effective in combatting inflammation and its complications Methods and Materials: A literature search was conducted, and articles published only in English, until December 2022 were included. The results are reported in the form of a narrative review. Results: The perioperative use of probiotics and/or symbiotics results in lower risk of infectious complications, including reduced rates of surgical site infections, respiratory and urinary tract infections, shorter hospital stays, and fewer days of antibiotic administration. It also contributes to reducing non-infectious complications, as it mitigates systemic and local inflammation via maintenance of the intestinal barrier, improves intestinal mobility, and is associated with lower rates of postoperative pain and anastomotic leak. Conclusions: Restoring gut microbiota after disruptions caused by surgery may accelerate local healing processes, attenuate systemic inflammation, and may thus prove beneficial to certain populations.

The implication of gut microbiota in recovery from gastrointestinal surgery

Recovery from gastrointestinal (GI) surgery is often interrupted by the unpredictable occurrence of postoperative complications, including infections, anastomotic leak, GI dysmotility, malabsorption, cancer development, and cancer recurrence, in which the implication of gut microbiota is beginning to emerge. Gut microbiota can be imbalanced before surgery due to the underlying disease and its treatment. The immediate preparations for GI surgery, including fasting, mechanical bowel cleaning, and antibiotic intervention, disrupt gut microbiota. Surgical removal of GI segments also perturbs gut microbiota due to GI tract reconstruction and epithelial barrier destruction. In return, the altered gut microbiota contributes to the occurrence of postoperative complications. Therefore, understanding how to balance the gut microbiota during the perioperative period is important for surgeons. We aim to overview the current knowledge to investigate the role of gut microbiota in recovery from GI surgery, focusing on the crosstalk between gut microbiota and host in the pathogenesis of postoperative complications. A comprehensive understanding of the postoperative response of the GI tract to the altered gut microbiota provides valuable cues for surgeons to preserve the beneficial functions and suppress the adverse effects of gut microbiota, which will help to enhance recovery from GI surgery.

Wound repair in sea urchin larvae involves pigment cells and blastocoelar cells

Sea urchin larvae spend weeks to months feeding on plankton prior to metamorphosis. When handled in the laboratory they are easily injured, suggesting that in the plankton they are injured with some frequency. Fortunately, larval wounds are repaired through an efficient wound response with mesenchymal pigment cells and blastocoelar cells assisting as the epithelium closes. An injury to the epithelium leads to an immediate calcium transient that rapidly spreads around the entire larva and is necessary for activating pigment cell migration toward the wound. If calcium transport is blocked, the pigment cells fail to activate and remain in place. When activated, pigment cells initiate directed migration to the wound site from distances of at least 85 ​μm. Upon arrival at the wound site they participate in an innate immune response. Blastocoelar cells are recruited to the injury site as well, though the calcium transient is unnecessary for activating these cells. At the wound site, blastocoelar cells participate in several functions including remodeling the skeleton if it protrudes through the epithelium.

IL-1-dependent enteric gliosis guides intestinal inflammation and dysmotility and modulates macrophage function

Muscularis Externa Macrophages (ME-Macs) and enteric glial cells (EGCs) are closely associated cell types in the bowel wall, and important interactions are thought to occur between them during intestinal inflammation. They are involved in developing postoperative ileus (POI), an acute, surgery-induced inflammatory disorder triggered by IL-1 receptor type I (IL1R1)-signaling. In this study, we demonstrate that IL1R1-signaling in murine and human EGCs induces a reactive state, named enteric gliosis, characterized by a strong induction of distinct chemokines, cytokines, and the colony-stimulating factors 1 and 3. Ribosomal tagging revealed enteric gliosis as an early part of POI pathogenesis, and mice with an EGC-restricted IL1R1-deficiency failed to develop postoperative enteric gliosis, showed diminished immune cell infiltration, and were protected from POI. Furthermore, the IL1R1-deficiency in EGCs altered the surgery-induced glial activation state and reduced phagocytosis in macrophages, as well as their migration and accumulation around enteric ganglia. In patients, bowel surgery also induced IL-1-signaling, key molecules of enteric gliosis, and macrophage activation. Together, our data show that IL1R1-signaling triggers enteric gliosis, which results in ME-Mac activation and the development of POI. Intervention in this pathway might be a useful prophylactic strategy in preventing such motility disorders and gut inflammation.

Shenhuang Plaster Application Improves Gastrointestinal Motility in Mice with Postoperative Ileus through Intestinal Microbiota

Postoperative ileus (POI) is a common surgical complication, and its incidence remains high. Shenhuang Plaster (SHP) is a famous traditional Chinese medicine with a definite curative effect on postoperative intestinal dysfunction; however, the mechanisms involved in these effects are unclear. Accordingly, in this study, we constructed a POI mouse model and used the intestinal flora as the target to explore the regulatory effect of SHP on gastrointestinal motility. The results illustrated that SHP applied at the Shenque acupoint promoted the recovery of gastrointestinal motility, relieved intestinal villus atrophy and basal damage caused by POI, protected the integrity of intestinal tissue morphology, and alleviated the inflammatory response in the intestinal tissue of POI model mice. In addition, we clarified the role of the intestinal flora in the occurrence and development of POI, further evaluated the changes in the intestinal flora in each group of mice, and analysed the regulatory effect of SHP on the intestinal flora in mice with POI. The results suggested that SHP might improve gastrointestinal motility disorder in POI mice by effectively regulating intestinal flora.

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 Microbiota and the Relationship with Colorectal Cancer: Surgical Complications—A Review

Colorectal cancer (CRC) is one of the most common cancers and represents a major global health burden. While genetics are implicated in a portion of CRC patients, most cases are sporadic. A new possibility of tumor initiation and promotion might be microbiome composition. It was recently shown that bacteria from the gut microbiome might be used as biomarkers for CRC detection, especially Fusobacterium nucleatum, Peptostreoptococcus stomatis, Parvimonas mica, Solobacterium moorei, and Peptostreptococcus anaerobius. Conversely, the healthy gut microbiome is mostly colonized by Bacterioides (Bacterioides fragilis, vulgatus, uniformis), Firmicutes (Clostridium spp., Ruminococcus faecis, Enterococcus faecium), and Actinobacteria (Bifidobacterium bifidum). Some strains of gut bacteria favor tumor promotion through DNA and RNA damage (directly or through interaction with other known food carcinogens) and through local immune inhibition. It is possible that bacteria (e.g., Bacillus polyfermenticus, Alistipes shahii, Lactobacillus casei) exist with protective functions against tumor promotion. Despite current advances in colorectal cancer treatment, especially in the medical oncology and radiotherapy domains, surgery remains the mainstay of curative treatment for colorectal cancer patients, even in the oligometastatic setting. Surgical complications like anastomotic leakage, excessive blood loss, abscess, and abdominal sepsis can reduce 1-year and 5-year overall survival and increase the recurrence rates for these patients; therefore, we reviewed currently published data focusing on the relationship between gut microbiota and postoperative complications for colorectal cancer patients.

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.

Dendritic cell functions in the inductive and effector sites of intestinal immunity

The intestine is constantly exposed to foreign antigens, which are mostly innocuous but can sometimes be harmful. Therefore, the intestinal immune system has the delicate task of maintaining immune tolerance to harmless food antigens while inducing tailored immune responses to pathogens and regulating but tolerating the microbiota. Intestinal dendritic cells (DCs) play a central role in these functions as sentinel cells able to prime and polarize the T cell responses. DCs are deployed throughout the intestinal mucosa but with local specializations along the gut length and between the diffuse effector sites of the gut lamina propria (LP) and the well-organized immune inductive sites comprising isolated lymphoid follicles (ILFs), Peyer's patches (PPs), and other species-specific gut-associated lymphoid tissues (GALTs). Understanding the specificities of each intestinal DC subset, how environmental factors influence DC functions, and how these can be modulated is key to harnessing the therapeutic potential of mucosal adaptive immune responses, whether by enhancing the efficacy of mucosal vaccines or by increasing tolerogenic responses in inflammatory disorders. In this review, we summarize recent findings related to intestinal DCs in steady state and upon inflammation, with a special focus on their functional specializations, highly dependent on their microenvironment.

Human Colonic Microbiota and Short-Term Postoperative Outcomes in Colorectal Cancer Patients: A Pilot Study

Despite the advances in surgical techniques and perioperative care, the complication rates after colorectal cancer surgery have remained stable. Recently, it has been suggested that colon microbiota may be implicated in several pathways that can lead to impaired colonic homeostasis and, thereby, to the development of complications after colorectal surgery. The aim of this study was to evaluate the potential impact of colonic dysbiosis on postoperative course. This prospective human clinical study recruited patients operated on for left colon, sigmoid colon or rectal cancer. Colon mucosa and fecal samples were collected to study mucosa associated microbiota (MAM) and luminal microbiota (LM), accordingly. Preliminary analysis for the first 25 consecutive patients with V3–V4 16S rRNA metagenomic analysis was performed. Bacterial composition and abundance in patients who developed postoperative complications over a 90-day follow-up period were compared to those without postoperative complications. Abundance and distribution of genera in MAM differed significantly when compared to LM with a significant impact on neoadjuvant therapy on bacterial composition. Preliminary analysis revealed no statistically significant differences in LM nor in MAM composition when individuals with and without postoperative surgical complications were compared. In cases of postoperative complications, LM and MAM showed significantly decreased diversity. Composition of the colonic microbiota is altered by neoadjuvant therapy. Results on the impact of colonic dysbiosis on postoperative complications are pending the end of the present study, with 50 patients enrolled.

Transcutaneous electrical acupoint stimulation applied in lower limbs decreases the incidence of paralytic ileus after colorectal surgery: A multicenter randomized controlled trial

BACKGROUND

Postoperative paralytic ileus prolongs hospitalization duration, increases medical expenses, and is even associated with postoperative mortality; however, effective prevention of postoperative paralytic ileus is not yet available. This trial aimed to assess the preventative effectiveness of transcutaneous electrical acupoint stimulation applied in the lower limbs on postoperative paralytic ileus incidence after colorectal surgery.

METHODS

After ethics approval and written informed consent, 610 patients from 10 hospitals who were scheduled for colorectal surgery between May 2018 and September 2019 were enrolled. Patients were randomly allocated into the transcutaneous electrical acupoint stimulation (stimulated on bilateral Zusanli, Shangjuxu, and Sanyinjiao acupoints in lower limbs for 30 minutes each time, total 4 times) or sham (without currents delivered) group with 1:1 ratio. The primary outcome was postoperative paralytic ileus incidence, defined as no flatus for >72 hours after surgery.

RESULTS

Compared to the sham treatment, transcutaneous electrical acupoint stimulation lowered the postoperative paralytic ileus incidence by 8.7% (32.3% vs 41.0%, P = .026) and decreased the risk of postoperative paralytic ileus by 32% (OR, 0.68; P = .029). Transcutaneous electrical acupoint stimulation also shortened the recovery time to flatus, defecation, normal diet, and bowel sounds. Transcutaneous electrical acupoint stimulation treatment significantly increased median serum acetylcholine by 55% (P = .007) and interleukin-10 by 88% (P < .001), but decreased interleukin-6 by 47% (P < .001) and inducible nitric oxide synthase by 42% (P = .002) at 72 hours postoperatively.

CONCLUSION

Transcutaneous electrical acupoint stimulation attenuated the postoperative paralytic ileus incidence and enhanced gastrointestinal functional recovery, which may be associated with increasing parasympathetic nerve tone and its anti-inflammatory actions.

SSAT State-of-the-Art Conference: Advancements in the Microbiome

The microbiome plays a major role in human physiology by influencing obesity, inducing inflammation, and impacting cancer therapies. During the 60th Annual Meeting of the Society of the Alimentary Tract (SSAT) at the State-of-the-Art Conference, experts in the field discussed the influence of the microbiome. This paper is a summary of the influence of the microbiome on obesity, inflammatory bowel disease, pancreatic cancer, cancer therapies, and gastrointestinal optimization. This review shows how the microbiome plays an important role in the development of diseases and surgical complications. Future studies are needed in targeting the gut microbiome to develop individualized therapies.

Niche-specific functional heterogeneity of intestinal resident macrophages

Intestinal resident macrophages are at the front line of host defence at the mucosal barrier within the gastrointestinal tract and have long been known to play a crucial role in the response to food antigens and bacteria that are able to penetrate the mucosal barrier. However, recent advances in single-cell RNA sequencing technology have revealed that resident macrophages throughout the gut are functionally specialised to carry out specific roles in the niche they occupy, leading to an unprecedented understanding of the heterogeneity and potential biological functions of these cells. This review aims to integrate these novel findings with long-standing knowledge, to provide an updated overview on our understanding of macrophage function in the gastrointestinal tract and to speculate on the role of specialised subsets in the context of homoeostasis and disease.

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.

Intervention on gut microbiota may change the strategy for management of colorectal cancer

Dysbiosis in the gut microbiota composition due to environmental or genetic variations can disrupt the immune system and may promote several diseases such as colorectal cancer (CRC). Gut microbiota can alter the toxicity and efficiency of an extensive range of CRC treatment methods, especially surgery, chemotherapy, radiotherapy, and immunotherapy. The recent scientific evidence suggested that gut microbiota modulation exhibits an essential positive influence on inhibition and treatment of CRC. The literature survey revealed that modulating the gut microbiota composition by probiotics, prebiotics, and diets protects CRC patients from treatment-associated adverse effects. This review summarizes the recent advancements in the association between interventions on gut microbiota and CRC to provide innovative strategies for enhancing the safety and efficiency of CRC therapy.

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.

Proteomic and bioinformatic profiling of neutrophils in CLL reveals functional defects that predispose to bacterial infections

Patients with chronic lymphocytic leukemia (CLL) typically suffer from frequent and severe bacterial infections. Although it is well known that neutrophils are critical innate immune cells facilitating the early defense, the underlying phenotypical and functional changes in neutrophils during CLL remain largely elusive. Using a murine adoptive transfer model of CLL, we demonstrate aggravated bacterial burden in CLL-bearing mice upon a urinary tract infection with uropathogenic Escherichia coli. Bioinformatic analyses of the neutrophil proteome revealed increased expression of proteins associated with interferon signaling and decreased protein expression associated with granule composition and neutrophil migration. Functional experiments validated these findings by showing reduced levels of myeloperoxidase and acidification of neutrophil granules after ex vivo phagocytosis of bacteria. Pathway enrichment analysis indicated decreased expression of molecules critical for neutrophil recruitment, and migration of neutrophils into the infected urinary bladder was significantly reduced. These altered migratory properties of neutrophils were also associated with reduced expression of CD62L and CXCR4 and correlated with an increased incidence of infections in patients with CLL. In conclusion, this study describes a molecular signature of neutrophils through proteomic, bioinformatic, and functional analyses that are linked to a reduced migratory ability, potentially leading to increased bacterial infections in patients with CLL.

The gut microbiota and colorectal surgery outcomes: facts or hype? A narrative review

BACKGROUND

The gut microbiota (GM) has been proposed as one of the main determinants of colorectal surgery complications and theorized as the "missing factor" that could explain still poorly understood complications. Herein, we investigate this theory and report the current evidence on the role of the GM in colorectal surgery.

METHODS

We first present the findings associating the role of the GM with the physiological response to surgery. Second, the change in GM composition during and after surgery and its association with colorectal surgery complications (ileus, adhesions, surgical-site infections, anastomotic leak, and diversion colitis) are reviewed. Finally, we present the findings linking GM science to the application of the enhanced recovery after surgery (ERAS) protocol, for the use of oral antibiotics with mechanical bowel preparation and for the administration of probiotics/synbiotics.

RESULTS

According to preclinical and translational evidence, the GM is capable of influencing colorectal surgery outcomes. Clinical evidence supports the application of an ERAS protocol and the preoperative administration of multistrain probiotics/synbiotics. GM manipulation with oral antibiotics with mechanical bowel preparation still has uncertain benefits in right-sided colic resection but is very promising for left-sided colic resection.

CONCLUSIONS

The GM may be a determinant of colorectal surgery outcomes. There is an emerging need to implement translational research on the topic. Future clinical studies should clarify the composition of preoperative and postoperative GM and the impact of the GM on different colorectal surgery complications and should assess the validity of GM-targeted measures in effectively reducing complications for all colorectal surgery locations.

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.

Prediction of Postoperative Ileus in Patients With Colorectal Cancer by Preoperative Gut Microbiota

Background

Ileus and postoperative ileus (POI) are common complications of colorectal cancer (CRC). However, little is known about the gut microbiota associated with ileus.

Method

Differences in gut microbiota were evaluated by 16S rRNA gene sequencing. We characterized the gut microbiota in 85 CRC patients (cohort 1) and detected differences, and an independent cohort composed of 38 CRC patients (cohort 2) was used to evaluate the results.

Results

The gut microbiota of CRC patients with and without ileus exhibited large differences in alpha- and beta-diversities and bacterial taxa. The Firmicutes-to-Bacteroidetes ratio and microbial dysbiosis index (MDI) showed greater dysbiosis among ileus patients than among those without ileus. According to the location of CRC, the difference in gut microbiota between patients with and without ileus was more obvious in those with distal CRC than in those with proximal CRC. Finally, Faecalibacterium was significantly reduced in the postoperative perioperative period in patients with ileus. Thus, we used Faecalibacterium as a biomarker for predicting perioperative or POI: the AUC value was 0.74 for perioperative ileus and 0.67 for POI that appeared at 6 months after hospital discharge. The predictive power was evaluated in Cohort 2, with an AUC value of 0.79.

Conclusion

These findings regarding difference of gut microbiota in postoperative CRC patients may provide a theoretical basis for the use of microbiota as biomarkers for the prediction of POI.

The Gut Microbiome and Individual-Specific Responses to Diet

Nutritional content and timing are increasingly appreciated to constitute important human variables collectively impacting all aspects of human physiology and disease. However, person-specific mechanisms driving nutritional impacts on the human host remain incompletely understood, while current dietary recommendations remain empirical and nonpersonalized. Precision nutrition aims to harness individualized bodies of data, including the human gut microbiome, in predicting person-specific physiological responses (such as glycemic responses) to food. With these advances notwithstanding, many unknowns remain, including the long-term efficacy of such interventions in delaying or reversing human metabolic disease, mechanisms driving these dietary effects, and the extent of the contribution of the gut microbiome to these processes. We summarize these conceptual advances, while highlighting challenges and means of addressing them in the next decade of study of precision medicine, toward generation of insights that may help to evolve precision nutrition as an effective future tool in a variety of "multifactorial" human disorders.

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.

Alterations of the Rectal Microbiome Are Associated with the Development of Postoperative Ileus in Patients Undergoing Colorectal Surgery

BACKGROUND

The most common complications after colorectal surgery, postoperative ileus, surgical site infections, and anastomotic leaks continue to occur despite advances in surgical technique and enhanced recovery pathways. Preclinical studies have documented that intestinal bacteria play a role in the development of these complication, yet human data is lacking. Here we hypothesized that patients that develop ileus, surgical site infection, and/or anastomotic leak following colorectal surgery harbor a specific preoperative gut microbiome.

METHODS

We performed a prospective cohort study on 101 patients undergoing colon or rectal resection at the Mayo Clinic. Rectal samples were collected preoperatively and on the ward on postoperative day two. The bacterial community from each sample was characterized by 16S rRNA and associated with the development of complications.

RESULTS

The rectal microbiome collected from patients in the operating room (p = .003) and on postoperative day two (p = .001) was significantly difference in patients whom later developed postoperative ileus compared with patients that had a normal return of bowel function. Patients whom developed ileus showed increased abundance of Bacteroides spp., Parabacteroides spp., and Ruminococcus spp., bacteria that are associated with promoting intestinal inflammation. There were no differences in the microbiome in patients that developed surgical site infections or anastomotic leaks.

CONCLUSIONS

In this pilot study, patients that develop postoperative ileus harbor a specific gut microbiome during the perioperative period. These findings demonstrate that the preoperative bacterial composition may predispose patients to the development of ileus and that perioperative manipulation of the gut bacteria may provide a novel method to promote normal return of bowel function.

Role of gut microbiota-immunity axis in patients undergoing surgery for colorectal cancer: Focus on short and long-term outcomes

Human body is colonized by a huge amount of microorganisms mostly located in the gastrointestinal tract. These dynamic communities, the environment and their metabolites constitute the microbiota. Growing data suggests a causal role of a dysbiotic microbiota in several pathologies, such as metabolic and neurological disorders, immunity dysregulations and cancer, especially the well-studied colorectal cancer development. However, many were preclinical studies and a complete knowledge of the pathogenetic mechanisms in humans is still absent. The gut microbiota can exert direct or indirect effects in different phases of colorectal cancer genesis. For example, Fusobacterium nucleatum promotes cancer through cellular proliferation and some strains of Escherichia coli and Bacteroides fragilis produce genotoxins. However, dysbiosis may also cause a pro-inflammatory state and the stimulation of a Th17 response with IL-17 and IL-22 secretion that have a pro-oncogenic activity, as demonstrated for Fusobacterium nucleatum. Microbiota has a crucial role in several stages of postoperative course; dysbiosis in fact seems related with surgical site infections and Enterococcus faecalis (and other collagenase-producers microbes) are suggested as a cause of anastomotic leak. Consequently, unbalanced presence of some species, together with altered immune response may also have a prognostic role. Microbiota has also a substantial role in effectiveness of chemotherapy, chemoresistance and in the related side effects. In other words, a complete knowledge of the fine pathological mechanisms of gut microbiota may provide a wide range of new diagnostic tools other than therapeutic targets in the light of tailored medicine.

Early oral nutrition improves postoperative ileus through the TRPA1/CCK1-R-mediated mast cell-nerve axis

Background

The mechanism of early oral nutrition that regulates the mast cell-nerve axis to improve postoperative ileus (POI) remains unclear. This study aims to investigate whether early oral nutrition can improve POI through Transient receptor potential ankyrin-1 (TRPA1)/cholecystokinin 1 receptor (CCK1-R) in the mast cell-nerve axis.

Methods

Experiment 1: Male Sprague-Dawley (SD) rats were randomly divided into the TRPA1 inhibitor + oral nutrition group (TI + ON + POI), oral nutrition group (ON + POI), POI group (POI) and sham surgery group (Sham). Nine rats in each group were treated. Experiment 2: Primary cultures of mast cells and dorsal root ganglion cells were created, and a non-contact co-culture system was established. The cells were divided into the dorsal root ganglion (DRG) group, mast cell group, DRG + mast cell group, TRPA1 inhibitor or enhancer group, mast cell stabilizer or enhancer group, CCK1-R inhibitor or enhancer group. The results of expression of TRPA1, CCK1-R and histamine in colon tissue, portal vein blood, supernatant or dorsal root ganglia, intestinal transport test and mast cell morphology were analysed.

Results

In experiment 1, Early oral nutrition could alleviate the degranulation and activation of mast cells and alleviate the inflammatory reaction of intestinal wall muscles (P<0.05). Early oral nutrition improved POI by stabilizing mast cells with TRPA1. TRPA1 inhibitor decreased CCK1-R concentrations in portal vein blood and CCK1-R expression in colonic smooth muscle (P<0.05). In experiment 2, the change in mast cell function regulated the secretion of CCK1-R by neurons, CCK1-R negatively regulated the degranulation and activation of mast cells (P<0.05), and mast cells positively regulated the expression of TRPA1 protein in DRG (P<0.05).

Conclusions

Early enteral nutrition can improve POI through the TRPA1/CCK1-R-mediated mast cell-nerve axis. TRPA1 positively regulates CCK1-R to stabilize mast cells, but TRPA1 is not the target of the downstream CCK1-R pathway.

Gut macrophages: key players in intestinal immunity and tissue physiology

The mammalian gastrointestinal tract harbors a large reservoir of tissue macrophages, which, in concert with other immune cells, help to maintain a delicate balance between tolerance to commensal microbes and food antigens, and resistance to potentially harmful microbes or toxins. Beyond their roles in resistance and tolerance, recent studies have uncovered novel roles played by tissue-resident, including intestinal-resident macrophages in organ physiology. Here, we will discuss recent advances in the understanding of the origin, phenotype and function of macrophages residing in the different layers of the intestine during homeostasis and under pathological conditions.

Sexual dimorphism in upper gastrointestinal motility is dependent on duration of fast, time of day, age, and strain of mice

BACKGROUND

An important limitation of gastrointestinal motility testing is high variability. Conditions that could contribute to variability, including the duration of pretest fasting and time of day, are rarely reported and have not been examined systematically. This study aimed to explore whether these conditions, as well as age, sex, and strain of mice, affect the results of a standard laboratory test of upper gastrointestinal motility.

METHODS

Male and female 8-week-old C57BL/6J mice received a gastric gavage of fluorescein isothiocyanate (FITC)-conjugated dextran. FITC-dextran distribution was measured 30 minutes later. Mean geometric centers (MGCs) were calculated to determine the effects of short versus prolonged fasting and morning versus afternoon testing. The influence of age was assessed in 2- to 10-week-old animals, and the influence of strain was determined in C57BL/6J, BALB/c, and CD-1 mice.

KEY RESULTS

Motility was sexually dimorphic. MGC progressed 19% further in 8-week-old C57BL/6J males versus females when tested in the morning after a short fast. Similar patterns were observed in morning or afternoon testing after overnight fasting. In males, motility was unaffected by time of day; however, MGC progressed 31% further in females tested in the afternoon versus morning after a short fast. Sex differences also were present in CD-1 but not BALB/c mice. Testing in neonates revealed strikingly low variability and no sex differences.

CONCLUSIONS & INFERENCES

Fasting duration, time of day, age, sex, and strain of mice all influence upper gastrointestinal motility testing. Sex differences are not present in neonatal pups, but develop soon after weaning.

AIM2 inflammasome-derived IL-1β induces postoperative ileus in mice

Postoperative ileus (POI) is an intestinal dysmotility frequently occurring after abdominal surgery. An orchestrated neuroimmune response within the muscularis externa (ME) involves activation of resident macrophages, enteric glia and infiltration of blood-derived leukocytes. Interleukin-1 receptor type-I (IL1R1) signalling on enteric glia has been shown to be involved in POI development. Herein we investigated the distinct role of the IL1R1 ligands interleukin (IL) -1α and IL-1β and focused on the mechanism of IL-1β production. IL-1α and IL-1β deficient mice were protected from POI. Bone-marrow transplantation studies indicated that IL-1α originated from radio-resistant cells while IL-1β was released from the radio-sensitive infiltrating leukocytes. Mouse strains deficient in inflammasome formation identified the absent in melanoma 2 (AIM2) inflammasome to be crucial for IL-1β production in POI. Mechanistically, antibiotic-treated mice revealed a prominent role of the microbiome in IL-1β production. Our study provides new insights into distinct roles of IL-1α and IL-1β signalling during POI. While IL-1α release is most likely an immediate passive response to the surgical trauma, IL-1β production depends on AIM2 inflammasome formation and the microbiome. Selective interaction in this pathway might be a promising target to prevent POI in surgical patients.

Increased susceptibility to oral Trichuris muris infection in the specific absence of CXCR5+ CD11c+ cells

Trichuris muris is a natural mouse helminth pathogen which establishes infection specifically in the caecum and proximal colon. The rapid expulsion of T. muris in resistant mouse strains is associated with the induction of a protective T helper cell type 2 (Th2)‐polarized immune response. Susceptible mouse strains, in contrast, mount an inappropriate Th1 response to T. muris infection. Expression of the chemokine CXCL13 by stromal follicular dendritic cells attracts CXCR5‐expressing cells towards the B‐cell follicles. Previous studies using a complex in vivo depletion model have suggested that CXCR5‐expressing conventional dendritic cells (cDC) help regulate the induction of Th2‐polarized responses. Here, transgenic mice with CXCR5 deficiency specifically restricted to CD11c⁺ cells were used to determine whether the specific absence CXCR5 on CD11c⁺ cells such as cDC would influence susceptibility to oral T. muris infection by affecting the Th1/Th2 balance. We show that in contrast to control mice, those which lacked CXCR5 expression on CD11c⁺ cells failed to clear T. muris infection and developed cytokine and antibody responses that suggested a disturbed Th1/Th2 balance with enhanced IFN‐γ expression. These data suggest an important role of CXCR5‐expressing CD11c⁺ cells such as cDC in immunity to oral T. muris infection.

Neuronal regulation of intestinal immune functions in health and disease

BACKGROUND

Nerve-mucosa interactions control various elements of gastrointestinal functions, including mucosal host defense, gut barrier function, and epithelial cell growth and differentiation. In both intestinal and extra-intestinal diseases, alterations of autonomic nerve activity have been observed to be concurrent with the disease course, such as in inflammatory and functional bowel diseases, and neurodegenerative diseases. This is relevant as the extrinsic autonomic nervous system is increasingly recognized to modulate gut inflammatory responses. The molecular and cellular mechanisms through which the extrinsic and intrinsic nerve pathways may regulate digestive mucosal functions have been investigated in several pre-clinical and clinical studies.

PURPOSE

The present review focuses on the involvement of neural pathways in gastrointestinal disease, and addresses the current strategies to intervene with neuronal pathway as a means of treatment.

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.

CD103+CD11b+ mucosal classical dendritic cells initiate long-term switched antibody responses to flagellin

Antibody responses induced at mucosal and nonmucosal sites demonstrate a significant level of autonomy. Here, we demonstrate a key role for mucosal interferon regulatory factor-4 (IRF4)-dependent CD103+CD11b+ (DP), classical dendritic cells (cDCs) in the induction of T-dependent immunoglobulin G (IgG) and immunoglobulin A (IgA) responses in the mesenteric lymph node (MLN) following systemic immunization with soluble flagellin (sFliC). In contrast, IRF8-dependent CD103+CD11b- (SP) are not required for these responses. The lack of this response correlated with a complete absence of sFliC-specific plasma cells in the MLN, small intestinal lamina propria, and surprisingly also the bone marrow (BM). Many sFliC-specific plasma cells accumulating in the BM of immunized wild-type mice expressed α4β7+, suggesting a mucosal origin. Collectively, these results suggest that mucosal DP cDC contribute to the generation of the sFliC-specific plasma cell pool in the BM and thus serve as a bridge linking the mucosal and systemic immune system.