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

MIR-155 PROMOTES ACUTE ORGAN INJURY IN LPS-INDUCED ENDOTOXEMIC MICE BY ENHANCING CCL-2 EXPRESSION IN MACROPHAGES

ABSTRACT

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Macrophages play important roles in the inflammatory process of sepsis by secreting chemokines. Chemokine (CC-motif) ligand 2 (CCL-2) is one of the main proinflammatory chemokines secreted by macrophages that plays a critical role in the recruitment of more monocytes and macrophages to the sites of injury in sepsis, but the mechanisms that regulate CCL-2 expression in macrophages during sepsis are still unknown. In the present study, by using the LPS-induced endotoxemia model, we found that LPS induced the expression of microRNA (miR)-155 and CCL-2 in endotoxemic mice and RAW264.7 cells. MiR-155 mimics or miR-155 inhibitor treatment experiment suggested that miR-155 was sufficient to increase LPS-induced CCL-2 expression in macrophages, but miR-155 was not the only factor promoting CCL-2 expression. We further demonstrated that miR-155-induced increase of CCL-2 promoted chemotaxis of additional macrophages, which subsequently enhanced lung injury in endotoxemic mice. Serum/glucocorticoid regulated kinase family member 3 (SGK3), a potential target of miR-155, was identified by RNA sequencing and predicted by TargetScan and miRDB. We further confirmed miR-155 regulated SGK3 to increase LPS-induced CCL-2 by using miR-155 mimics and SGK3 overexpression. Thus, our study demonstrates that miR-155 targets SGK3 to increase LPS-induced CCL-2 expression in macrophages, which promotes macrophage chemotaxis and enhances organs injury during endotoxemia. Our study contributed to a better understanding of the mechanisms underlying the inflammatory response during sepsis.

The roles of tissue resident macrophages in health and cancer

As integral components of the immune microenvironment, tissue resident macrophages (TRMs) represent a self-renewing and long-lived cell population that plays crucial roles in maintaining homeostasis, promoting tissue remodeling after damage, defending against inflammation and even orchestrating cancer progression. However, the exact functions and roles of TRMs in cancer are not yet well understood. TRMs exhibit either pro-tumorigenic or anti-tumorigenic effects by engaging in phagocytosis and secreting diverse cytokines, chemokines, and growth factors to modulate the adaptive immune system. The life-span, turnover kinetics and monocyte replenishment of TRMs vary among different organs, adding to the complexity and controversial findings in TRMs studies. Considering the complexity of tissue associated macrophage origin, macrophages targeting strategy of each ontogeny should be carefully evaluated. Consequently, acquiring a comprehensive understanding of TRMs' origin, function, homeostasis, characteristics, and their roles in cancer for each specific organ holds significant research value. In this review, we aim to provide an outline of homeostasis and characteristics of resident macrophages in the lung, liver, brain, skin and intestinal, as well as their roles in modulating primary and metastatic cancer, which may inform and serve the future design of targeted therapies.

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.

Bile pigments in emergency and critical care medicine

Bile pigments, such as bilirubin and biliverdin, are end products of the heme degradation pathway in mammals and are widely known for their cytotoxic effects. However, recent studies have revealed that they exert cytoprotective effects through antioxidative, anti-inflammatory, and immunosuppressive properties. All these mechanisms are indispensable in the treatment of diseases in the field of emergency and critical care medicine, such as coronary ischemia, stroke, encephalomyelitis, acute lung injury/acute respiratory distress syndrome, mesenteric ischemia, and sepsis. While further research is required before the safe application of bile pigments in the clinical setting, their underlying mechanisms shed light on their utilization as therapeutic agents in the field of emergency and critical care medicine. This article aims to summarize the current understanding of bile pigments and re-evaluate their therapeutic potential in the diseases listed above.

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.

Inflammatory modulation and outer membrane vesicles (OMV) production associated to Bacteroides fragilis response to subinhibitory concentrations of metronidazole during experimental infection

OBJECTIVE

An experimental infection based on a tissue cage model was reproduced to evaluate the interference subinhibitory concentration (SIC) of metronidazole in Bacteroides fragilis OMV production patterns and immunological and histological characteristics of the host facing the experimental challenge.

METHODS

A tissue cage model was reproduced for B. fragilis experimental challenge in three Wistar rats groups: negative control group (NC) without bacterial inoculation; positive control group (PC) infected with parental strain; and experimental group (EG) infected with the parental strain and treated with metronidazole SIC. Tissue cage sections and histological preparations were evaluated under optical and transmission electron microscope. Observations included OMV identification and count and cellular envelope evaluation. Transcriptional analyses were performed to evaluate cytokines expression levels.

RESULTS

Total counts of leukocytes and neutrophils were higher for EG, and slight increase in PC group. It was observed an exacerbated inflammatory infiltrate after 8 days on infection. The expression of TNF-α was increased during the experiments, along with IL-1α and IL-6. MCP-1 levels were suppressed in almost every evaluated time-point. The IL-10 was exacerbated in EG group. A massive production and release of OMV and cell wall thickening were observed especially the EG group.

CONCLUSIONS

Despite literature data suggest positive association between OMV and antimicrobial stress for Gram negatives, no correlations are made for B. fragilis and drug-response during experimental model of infection. Results corroborate observations in which OMV may be involved in bacterial pathogenicity once the phenomenon was observed along histological evidence of exacerbated inflammation and cytokines modulation.

Activation of α7nAChR Protects Against Gastric Inflammation and Dysmotility in Parkinson's Disease Rats

The cholinergic anti-inflammatory pathway (CAIP) has been proposed to regulate gastrointestinal inflammation via acetylcholine released from the vagus nerve activating α7 nicotinic receptor (α7nAChR) on macrophages. Parkinson’s disease (PD) patients and PD rats with substantia nigra (SN) lesions exhibit gastroparesis and a decayed vagal pathway. To investigate whether activating α7nAChR could ameliorate inflammation and gastric dysmotility in PD rats, ELISA, western blot analysis, and real-time PCR were used to detect gastric inflammation. In vitro and in vivo gastric motility was investigated. Proinflammatory mediator levels and macrophage numbers were increased in the gastric muscularis of PD rats. α7nAChR was located on the gastric muscular macrophages of PD rats. The α7nAChR agonists PNU-282987 and GTS-21 decreased nuclear factor κB (NF-κB) activation and monocyte chemotactic protein-1 mRNA expression in the ex vivo gastric muscularis of PD rats, and these effects were abolished by an α7nAChR antagonist. After treatment with PNU-282987 in vivo, the PD rats showed decreased NF-κB activation, inflammatory mediator production, and contractile protein expression and improved gastric motility. The present study reveals that α7nAChR is involved in the development of gastroparesis in PD rats and provides novel insight for the treatment of gastric dysmotility in PD patients.

Potentilla discolor ameliorates LPS-induced inflammatory responses through suppressing NF-κB and AP-1 pathways

Potentilla discolor Bunge (PD) is a traditional Chinese medicine which has been widely used for the treatment of various inflammatory diseases (e.g., diarrhea, fever and furuncle). However, few studies focused on its effect on classical inflammation. This study aimed to investigate the anti-inflammatory effect and potential mechanism of the ethanol extract of the whole herbs of PD (EPD) in lipopolysaccharide (LPS)-induced inflammatory models. The obtained results showed that EPD decreased supernatant NO, tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) in LPS-activated RAW264.7 cells and mouse peritoneal macrophages. Moreover, its effect on NO was attributed to the suppression of iNOS expression rather than its activity. At the transcriptional level, EPD suppressed iNOS, TNF-α and MCP-1 mRNA expressions in LPS-stimulated RAW264.7 cells. Further study showed that EPD didn't affect the phosphorylation and degradation of IκBα, but yet impeded the nuclear translocation of p65 to inhibit NF-κB activation. Meanwhile, it also prevented JNK, ERK1/2 and p38 phosphorylation to dampen the activation of AP-1. In endotoxemia mouse model, EPD not only decreased interleukin-6, TNF-α and MCP-1 levels in serum, but also potently ameliorated diarrhea. These findings provide the theoretical basis for PD to treat inflammatory diseases, especially intestinal inflammation.

Postoperative ileus-An ongoing conundrum

BACKGROUND

Postoperative ileus is common and is a major clinical problem. It has been widely studied in patients and in experimental models in laboratory animals. A wide variety of treatments have been tested to prevent or modify the course of this disorder.

PURPOSE

This review draws together information on animal studies of ileus with studies on human patients. It summarizes some of the conceptual advances made in understanding the mechanisms that underlie paralytic ileus. The treatments that have been tested in human subjects (both pharmacological and non-pharmacological) and their efficacy are summarized and graded consistent with current clinical guidelines. The review is not intended to provide a comprehensive overview of ileus, but rather a general understanding of the major clinical problems associated with it, how animal models have been useful to elucidate key mechanisms and, finally, some perspectives from both scientists and clinicians as to how we may move forward with this debilitating yet common condition.

Use of quantitative real-time PCR to determine the local inflammatory response in the intestinal mucosa and muscularis of horses undergoing small intestinal resection

BACKGROUND

Studies in rodents and humans have demonstrated that intestinal manipulation or surgical trauma initiates an inflammatory response in the intestine which results in leucocyte recruitment to the muscularis externa causing smooth muscle dysfunction.

OBJECTIVES

To examine the intestinal inflammatory response in horses undergoing colic surgery by measuring relative differential gene expression in intestinal tissues harvested from surgical colic cases and control horses.

STUDY DESIGN

Prospective case-control study.

METHODS

Mucosa and muscularis externa were harvested from healthy margins of resected small intestine from horses undergoing colic surgery (n = 12) and from intestine derived from control horses euthanised for reasons unrelated to the gastrointestinal tract (n = 6). Tissue was analysed for genes encoding proteins involved in the inflammatory response: interleukin (IL) 6 and IL1β, C-C motif chemokine ligand 2 (CCL2), tumour necrosis factor (TNF), prostaglandin-endoperoxide synthase 2 (PTGS2) and indoleamine 2,3-dioxygenase (IDO1). Relative expression of these genes was compared between the two groups. Further analysis was applied to the colic cases to determine whether the magnitude of relative gene expression was associated with the subsequent development of post-operative reflux (POR).

RESULTS

Samples obtained from colic cases had increased relative expression of IL1β, IL6, CCL2 and TNF in the mucosa and muscularis externa when compared with the control group. There was no difference in relative gene expression between proximal and distal resection margins and no association between duration of colic, age, resection length, short-term survival and the presence of pre-operative reflux and the relative expression of the genes of interest. Horses that developed POR had significantly greater relative gene expression of TNF in the mucosa compared with horses that did not develop POR.

MAIN LIMITATIONS

Small sample size per group and variation within the colic cases.

CONCLUSIONS

These preliminary data support an upregulation of inflammatory genes in the intestine of horses undergoing colic surgery.

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.

Ethanol extract of Elephantopus scaber Linn. Attenuates inflammatory response via the inhibition of NF-κB signaling by dampening p65-DNA binding activity in lipopolysaccharide-activated macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Elephantopus scaber Linn. (E.scaber) is a widely-used traditional herb whose use has been documented for various inflammatory diseases such as fever, sore throat, dysentery, carbuncle and so on. However, the effect and mechanism of E.scaber in LPS-activated macrophages remain unclear.

AIM

This study aims to investigate the anti-inflammatory mechanism of the ethanol extract of E.scaber (ESE) in lipopolysaccharide (LPS)-induced inflammatory models.

MATERIALS AND METHODS

Griess reagent was used to determine NO production, and the levels of TNF-α, IL-6, MCP-1 and IL-1β were determined by ELISA kits. The molecular mechanism research was performed by RT-PCR, Western blot, and electrophoretic mobility shift assay (EMSA). LPS-induced endotoxemia mouse model was used for evaluating the in vivo anti-inflammatory action of ESE.

RESULTS

ESE suppressed LPS-induced iNOS, TNF-α, IL-6, MCP-1 and IL-1β transcription as well as supernatant NO, TNF-α, IL-6, MCP-1 and IL-1β production in macrophages. Although ESE inhibited NF-κB activation, it did not affect the IκBα phosphorylation and degradation and the NF-κB p65 nuclear translocation. The result of EMSA revealed that ESE inhibited the NF-κB p65-DNA binding activity. Additionally, ESE also decreased the proinflammatory cytokines in serum and peritoneal lavage fluid of LPS-induced endotoxemic mice.

CONCLUSION

ESE has a potently anti-inflammatory effect through inhibiting the NF-κB p65-DNA binding activity in LPS-activated macrophages.

Ongoing inflammation enhances the toxicity of engineered nanomaterials: Application of an in vitro co-culture model of the healthy and inflamed intestine

Chronic inflammatory conditions can negatively impact intestinal barrier function and affect the epithelium's interaction with nano-sized materials. We demonstrate the application of a Caco-2/THP-1 co-culture mimicking the intestine in healthy (i.e. stable) or inflamed state in nanotoxicological research. The co-cultures were exposed to non-toxic concentrations of silver nanoparticles (AgNPs) or silver nitrate (AgNO3) for 24 h. The barrier integrity and cytokine release as well as necrotic and apoptotic cell death were investigated. AgNPs and AgNO3 most strongly affected the inflamed co-culture. Higher concentrations of AgNPs induced a significant increase in barrier integrity in the inflamed but not the stable co-culture. Necrotic and apoptotic cell death was detected in both conditions but were significantly more pronounced in the inflamed condition. The exposure to AgNO3 affected barrier integrity in all experimental set-ups, but caused nuclear condensation only in the Caco-2 monoculture and the inflamed co-culture. AgNPs reduced the release of monocyte chemoattractant protein-1 in the stable model. Clear differences were observed in the effects of AgNPs and AgNO3 in relation to the model's health status. The results suggest an increased vulnerability of the inflamed epithelial barrier towards AgNPs underlining the importance to consider the intestinal health status in the safety assessment of nanomaterials.

A new zinc chelator, IPZ-010 ameliorates postoperative ileus

Zinc was discovered to be a novel second messenger in immunoreactive cells. We synthesized a novel free zinc chelator, IPZ-010. Here, we investigated the effects of IPZ-010 in a mouse postoperative ileus model and determined the effects of zinc signal inhibition as a new therapeutic strategy against postoperative ileus. Zinc waves were measured in bone marrow-derived mast cells (BMMCs) loaded with a zinc indicator, Newport green. Degranulation and cytokine expression were measured in BMMCs and bone marrow-derived macrophages (BMDMs). Postoperative ileus model mice were established with intestinal manipulation. Mice were treated with IPZ-010 (30 mg/kg, s.c. or p.o.) 1 h before and 2 h and 4 h after intestinal manipulation. Gastrointestinal transit, inflammatory cell infiltration, and expression of inflammatory mediators were measured. Free zinc waves occurred following antigen stimulation in BMMCs and were blocked by IPZ-010. IPZ-010 inhibited interleukin-6 secretion and degranulation in BMMCs. IPZ-010 inhibited tumor necrosis factor-α mRNA expression in BMMCs stimulated with lipopolysaccharide or adenosine triphosphate, whereas IPZ-010 had no effects on tumor necrosis factor-α mRNA expression in BMDMs stimulated with lipopolysaccharide or adenosine triphosphate. In postoperative ileus model mice, IPZ-010 inhibited leukocyte infiltration and cytokine expression, which ameliorated gastrointestinal transit. Furthermore, ketotifen (1 mg/kg) induced similar effects as IPZ-010. These effects were not amplified by co-administration of IPZ-010 and ketotifen. IPZ-010 inhibited zinc waves, resulting in inhibition of inflammatory responses in activated BMMCs in vitro. Targeting zinc waves in inflammatory cells may be a novel therapeutic strategy for treating postoperative ileus.

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.

Distinct Chemokine Dynamics in Early Postoperative Period after Open and Robotic Colorectal Surgery

Stress response to robot-assisted colorectal surgery is largely unknown. Therefore, we conducted a prospective comparative nonrandomized study evaluating the perioperative dynamics of chemokines: IL-8/CXCL8, MCP-1/CCL2, MIP-1α/CCL3, MIP-1β/CCL4, RANTES/CCL5, and eotaxin-1/CCL11 in 61 colorectal cancer patients following open colorectal surgery (OCS) or robot-assisted surgery (RACS) in reference to clinical data. Postoperative IL-8 and MCP-1 increase was reduced in RACS with a magnitude of blood loss, length of surgery, and concomitant up-regulation of IL-6 and TNFα as its independent predictors. RANTES at 8 h dropped in RACS and RANTES, and MIP1α/β at 24 h were more elevated in RACS than OCS. IL-8 and MCP-1 at 72 h remained higher in patients subsequently developing surgical site infections, in whom a 2.6- and 2.5-fold increase was observed. IL-8 up-regulation at 24 h in patients undergoing open procedure was predictive of anastomotic leak (AL; 94% accuracy). Changes in MCP-1 and RANTES were predictive of delayed restoration of bowel function. Chemokines behave differently depending on procedure. A robot-assisted approach may be beneficial in terms of chemokine dynamics by favoring Th1 immunity and attenuated angiogenic potential and postoperative ileus. Monitoring chemokine dynamics may prove useful for predicting adverse clinical events. Attenuated chemokine up-regulation results from less severe blood loss and diminished inflammatory response.

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 Gut Microbiota-Gut Hormone Axis in the Pathophysiology of Functional Gastrointestinal Disorders

Gut microbiota exert a pivotal influence on various functions including gastrointestinal (GI) motility, metabolism, nutrition, immunity, and the neuroendocrine system in the host. These effects are mediated by not only short-chain fatty acids produced by microbiota but also gut hormones and inflammatory signaling by enteroendocrine and immune cells under the influence of the microbiota. GI motility is orchestrated by the enteric nervous system and hormonal networks, and disturbance of GI motility plays an important role in the pathophysiology of functional gastrointestinal disorders (FGIDs). In this context, microbiota-associated mediators are considered to act on specific receptors, thus affecting the enteric nervous system and, subsequently, GI motility. Thus, the pathophysiology of FGIDs is based on alterations of the gut microbiota/gut hormone axis, which have crucial effects on GI motility.

Association between gastrointestinal motility and macrophage/mast cell distribution in mice during the healing stage after DSS‑induced colitis

Irritable bowel syndrome (IBS) frequently occurs after infectious colitis or inflammatory bowel disease in patients with complete remission. This suggests that post‑inflammation‑associated factors may serve a role in the pathophysiology of IBS; however, the mechanism responsible remains unclear. In the present study, the involvement of macrophages and mast cells in alteration of gastrointestinal (GI) motility was investigated in mice in the remission stage after acute colitis. C57BL/6 mice were administered 2% dextran sulfate sodium in drinking water for 5 days and their intestinal tissues were investigated at intervals for up to 24 weeks. Expression of the mannose receptor (MR) and tryptase was examined by immunohistochemistry, and the GI transit time (GITT) was measured by administration of carmine red solution. A minimal degree of inflammatory cell infiltration persisted in the colon and also the small intestine of mice in remission after colitis and the GITT was significantly shorter. The number of muscularis MR‑positive macrophages was significantly increased in the small intestine of mice in remission after colitis and negatively correlated with GITT. Furthermore, results indicated that the number of muscularis tryptase‑positive mast cells was significantly increased throughout the intestine of mice during the healing process after colitis and was positively correlated with GITT. The present findings suggested an increased number of macrophages and/or mast cells in the intestinal muscular layer may be associated with the pathophysiology of GI dysmotility after colitis.

Muscularis macrophages: Key players in intestinal homeostasis and disease

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

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Muscularis macrophages communicate with enteric neurons in a bidirectional matter.

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

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Current challenges are to decipher therapeutic potentials of muscularis macrophages.

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

STAT3-RXR-Nrf2 activates systemic redox and energy homeostasis upon steep decline in pO2 gradient

Hypobaric hypoxia elicits several patho-physiological manifestations, some of which are known to be lethal. Among various molecular mechanisms proposed so far, perturbation in redox state due to imbalance between radical generation and antioxidant defence is promising. These molecular events are also related to hypoxic status of cancer cells and therefore its understanding has extended clinical advantage beyond high altitude hypoxia. In present study, however, the focus was to understand and propose a model for rapid acclimatization of high altitude visitors to enhance their performance based on molecular changes. We considered using simulated hypobaric hypoxia at some established thresholds of high altitude stratification based on known physiological effects. Previous studies have focused on the temporal aspect while overlooking the effects of varying pO₂ levels during exposure to hypobaric hypoxia. The pO₂ levels, indicative of altitude, are crucial to redox homeostasis and can be the limiting factor during acclimatization to hypobaric hypoxia. In this study we present the effects of acute (24h) exposure to high (3049m; pO₂: 71kPa), very high (4573m; pO₂: 59kPa) and extreme altitude (7620m; pO₂: 40kPa) zones on lung and plasma using semi-quantitative redox specific transcripts and quantitative proteo-bioinformatics workflow in conjunction with redox stress assays. It was observed that direct exposure to extreme altitude caused 100% mortality, which turned into high survival rate after pre-exposure to 59kPa, for which molecular explanation were also found. The pO₂ of 59kPa (very high altitude zone) elicits systemic energy and redox homeostatic processes by modulating the STAT3-RXR-Nrf2 trio. Finally we posit the various processes downstream of STAT3-RXR-Nrf2 and the plasma proteins that can be used to ascertain the redox status of an individual.

Dynamics of M1 macrophages in oral mucosal lesions during the development of acute graft-versus-host disease in rats

The role of macrophage infiltrates in oral mucosal acute graft-versus-host disease (AGVHD) remains unclear, although clinical studies suggest that macrophage infiltration correlates directly with the severity of AGVHD. In this study, we investigated the role of M1 macrophage infiltration in the oral mucosa of rats with AGVHD. Lewis rat spleen cells were injected into (Lewis × Brown Norway) F₁ rats to induce systemic GVHD. Tongue samples were evaluated using histology, immunohistochemistry, dual immunofluorescence, real-time reverse transcription-polymerase chain reaction, Transwell migration assays and Stamper-Woodruff binding assays. At the onset of oral mucosal AGVHD, dual immunofluorescence and migration assays revealed that M1 macrophages had accumulated in the basement membrane (BM) region via the laminin/CD29 β1 integrin pathway. Macrophage-secreted matrix metalloproteinase-2 was related to BM degradation. The adhesion of macrophages to the oral epithelium could be inhibited by pretreating macrophages with a CC chemokine receptor 2 (CCR2) antibody and/or pretreating lesion sections with monocyte chemoattractant protein-1 (MCP-1) antibody. Our data show that the migration and adhesion of M1 macrophages are associated with oral mucosal AGVHD, which is mediated in part by both laminin/CD29 β 1 intern and MCP-1/CCR2 pathways. Therefore, our study provides additional support for the contribution of macrophage infiltrate to the development of oral mucosal AGVHD.

Association study of MCP-1 promoter polymorphisms with the susceptibility and progression of sepsis

Previous studies have indicated that the monocyte chemo-attractant protein 1 (MCP-1), also referred to as C-C motif chemokine ligand 2 (CCL2), plays a significant role in the pathogenesis of sepsis, and this study investigated the clinical relevance of two MCP-1 gene polymorphisms on sepsis onset and progression. The Multiplex SNaPshot genotyping method was used to detect MCP-1 gene polymorphisms in the Chinese Han population (403 sepsis patients and 400 controls). MCP-1 mRNA expression levels were measured using real-time quantitative PCR, and enzyme-linked immunosorbent assays were used to analyze MCP-1, tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6) and interleukin-1 beta (IL-1β) plasma concentrations. The rs1024611 polymorphism analysis showed lower frequencies of minor homozygous genotype (AA) and allele (A) in sepsis patients compared to the healthy controls (19.4% vs. 31.5%, P = 0.0001 and 45.9% vs. 54.8%, P = 0.0004, respectively). And the frequencies of GG genotype and G allele were lower in sepsis patients compared to the controls (19.6% vs. 31.3%, P = 0.0002 and 46.0% vs. 54.5%, P = 0.0007, respectively). The rs1024611 AG/GG and rs2857656 GC/CC genotypes were both overrepresented in patients with severe sepsis (both P = 0.0005) and septic shock (P = 0.010 and P = 0.015, respectively) compared to the patients with mild sepsis. Moreover, among sepsis patients, the rs1024611 AG/GG and rs2857656 GC/CC carriers exhibited significant increases in expression levels of MCP-1 (P = 0.025), TNF-α (P = 0.034) and IL-6 (P = 0.043) compared with the rs1024611 AA or rs2857656 GG carriers. This study provides valuable clinical evidence that the MCP-1/CCL2 polymorphisms rs1024611 and rs2857656 are associated with sepsis susceptibility and development. We conclude that MCP-1/CCL2 plays a significant role in the pathogenesis of sepsis, which has potentially important therapeutic implications.

Neutrophil Accumulation in the Small Intestine Contributes to Local Tissue Destruction Following Combined Radiation and Burn Injury

The threat of nuclear disaster makes combined radiation and burn injury (CRI) a relevant topic when discussing modern trauma, as burn injuries are likely to occur with detonation of a conventional nuclear weapon. Previous studies in a murine model have shown that there is a breakdown of the gut epithelium and subsequent bacterial translocation into mesenteric lymph nodes after CRI. This study examines the early innate immune response of the small intestine after CRI. Using a previously established murine model of 5 to 5.5 Gy total body irradiation combined with 15% TBSA burn, the injury response of the small intestine was examined at 24, 48, and 72 hours by visual assessment, myeloperoxidase, and cytokine measurement. At 24 hours, intestinal damage as measured by villus blunting, crypt debris, and decreased mitosis, was apparent in all injury groups but the derangements persisted out to 72 hours only with CRI. The prolonged intestinal damage in CRI was accompanied by a 2-fold (P < .05) elevation in myeloperoxidase activity over sham animals at 48 hours and persisted as a 3-fold (P < .05) elevation at 72 hours after injury. Corresponding levels of KC were 8-fold (P < .05) higher than sham at 48 hours with persistent elevation at 72 hours. An enhanced innate immune response, partially mediated by the influx of neutrophils into the gastrointestinal tract is contributing to the hyperinflammatory state seen after CRI. Attenuation of the local gastrointestinal inflammatory response may play a major role in managing victims after nuclear disaster.

Inhaled hydrogen ameliorates endotoxin-induced bowel dysfunction

Aim

Gastrointestinal dysmotility frequently occurs during sepsis and multiple organ failure, remaining a major cause of morbidity and mortality in critically ill patients. Previous studies have shown that hydrogen, a new therapeutic gas, can improve various organ damage associated with sepsis. In this study, we investigated the protective efficacies of inhaled hydrogen against lipopolysaccharide (LPS)‐induced ileus.

Methods

Sepsis was induced in rats and mice by a single i.p. injection of LPS at 15 mg/kg for mice and 5 mg/kg for rats. Four groups of rats and mice including sham/air, sham/hydrogen, LPS/air, and LPS/hydrogen were analyzed. Hydrogen (1.3%) was inhaled for 25 h beginning at 1 h prior to LPS treatment. Gastrointestinal transit was quantified and cytokine levels, as well as neutrophil extravasation, in the intestinal muscularis propria were determined.

Results

Lipopolysaccharide challenge remarkably delayed gastrointestinal transit of non‐absorbable dextran, associated with increased leukocyte recruitment and upregulation of pro‐inflammatory cytokine mRNA expressions in the muscularis propria. Hydrogen significantly prevented LPS‐induced bowel dysmotility and reduced leukocyte extravasation, as well as inhibition of inflammatory cytokine expression. In vitro analysis of cytokine levels after LPS treatment of cultured macrophages showed an increase of interleukin‐10 by hydrogen regardless of the presence of nitric oxide.

Conclusions

This study showed the protective effects of hydrogen inhalation on LPS‐induced septic ileus through inhibition of inflammation in the muscularis propria. These inhibitory effects on the pro‐inflammatory response may be partially derived from anti‐inflammatory cytokine interleukin‐10 induction.

Intrinsic Gastrointestinal Macrophages: Their Phenotype and Role in Gastrointestinal Motility

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

Nepetaefuran and leonotinin isolated from Leonotis nepetaefolia R. Br. potently inhibit the LPS signaling pathway by suppressing the transactivation of NF-κB

Leonotis nepetaefolia R. Br., also known as Klip Dagga or Lion's Ear, has traditionally been used as a folk medicine to treat inflammatory diseases such as rheumatism, bronchitis, and asthma; however, the components that exhibit its anti-inflammatory activity have not yet been identified. In the present study, we investigated the effects of three types of diterpenoids, nepetaefuran, leonotinin, and leonotin, which were isolated from L. nepetaefolia R. Br., on the LPS signaling pathway in order to elucidate the anti-inflammatory mechanism involved. Nepetaefuran more potently inhibited the LPS-induced production of NO and CCL2 than leonotinin by suppressing the expression of iNOS mRNA and CCL2 mRNA. On the other hand, leonotin failed to inhibit the production of NO and CCL2 induced by LPS. Although nepetaefuran and leonotinin had no effect on the LPS-induced degradation of IκBα or nuclear translocation of NF-κB p65, they markedly inhibited the transcriptional activity of NF-κB. Nepetaefuran and leonotinin also inhibited the transcriptional activity of the GAL4-NF-κB p65 fusion protein. On the other hand, nepetaefuran, leonotinin and leonotin did not affect the LPS-induced activation of MAP kinase family members such as ERK, p38, and JNK. In addition, inhibitory effect of nepetaefuran and leonotinin on NF-κB activation is well correlated with their ability to induce activation of Nrf2 and ER stress. Taken together, these results demonstrated that nepetaefuran and leonotinin could be the components responsible for the anti-inflammatory activity of L. nepetaefolia R. Br. by specifically inhibiting the LPS-induced activation of NF-κB.

Enhanced monocyte chemoattractant protein-1 production in aging mice exaggerates cardiac depression during endotoxemia

Introduction

Endotoxemia and the systemic inflammatory response syndrome have a significant impact on post-surgery outcome, particularly in the elderly. The cytokine response to endotoxin is altered by aging. We tested the hypothesis that vulnerability to endotoxemic cardiac depression increases with aging due to age-related augmentation of myocardial inflammatory responses.

Methods

Adult (4 to 6 months) and old (20 to 22 months) C57/BL6 mice were treated with endotoxin (0.5 mg/kg, iv). Left ventricle (LV) function was assessed using a microcatheter system. Chemokines and cytokines in plasma and myocardium were analyzed by enzyme-linked immunosorbent assay (ELISA). Mononuclear cells in the myocardium were examined using immunofluorescence staining.

Results

Old mice displayed worse LV function (cardiac output: 3.0 ± 0.2 mL/min versus 4.4 ± 0.3 mL/min in adult mice) following endotoxin treatment. The exaggerated cardiac depression in old mice was associated with higher levels of monocyte chemoattractant protein-1 (MCP-1) and keratinocyte chemoattractant (KC) in plasma and myocardium, greater myocardial accumulation of mononuclear cells, and greater levels of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β) and interleukin 6 (IL-6) in plasma and myocardium. Neutralization of MCP-1 resulted in greater reductions in myocardial mononuclear cell accumulation and cytokine production, and greater improvement in LV function in old mice while neutralization of KC had a minimal effect on LV function.

Conclusion

Old mice have enhanced inflammatory responses to endotoxemia that lead to exaggerated cardiac functional depression. MCP-1 promotes myocardial mononuclear cell accumulation and cardiodepressant cytokines production, and plays an important role in the endotoxemic cardiomyopathy in old mice. The findings suggest that special attention is needed to protect the heart in the elderly with endotoxemia.

Induction of chemokines and cytokines before neutrophils and macrophage recruitment in different regions of rat liver after TAA administration

Single-dose thioacetamide (TAA) administration induces inflammation and acute liver damage. The mechanism of inflammatory cell recruitment in the liver is still unclear. The aim of this study was to examine the sequence and recruitment of inflammatory cells in different liver regions in relation to CXC- and CC-chemokine and cytokine expression during acute liver injury. Single-dose TAA was administered to rats intraperitoneally, and animals were killed at different time points thereafter. Serum and liver tissue were taken and frozen immediately. Tissue was used for immunostaining cryostat sections, RNA, and protein extraction. RT-PCR and western blotting were performed for RNA and protein analysis, respectively. An early increase (3 h) in CXCL8/IL-8 levels was measured followed by a marked release in MCP1/CCL2 (24 h) serum levels after TAA administration compared with controls. Similarly, an early increase in specific RNA of hepatic chemokines CXCL1/KC and CXCL8/IL-8 was found at 3 h, followed by an upregulation of CXCL5/LIX (6 h), CXCL2/MIP-2 (12 h), and MCP1/CCL2 gene expression at 24-48 h. Further, an induction of pro-inflammatory cytokines IFN-γ and IL-1β followed by IL-6 and TNF-α was observed with a maximum at 12 h. The magnitude of increase in gene expression of TNF-α and MCP1/CCL2 was the highest among all cytokines and chemokines, respectively. By means of immunohistochemistry, an early (12-24 h) increase in the number of only neutrophil granulocytes (NGs) attached to and around portal vessel walls was observed, followed by increased numbers of mononuclear phagocytes (24-48 h) along the sinusoids. Treatment of the human monocytic cell line U-937 with TNF-α increased the gene expression of CXCL1/KC, CXCL8/IL-8, and MCP1/CCL2. Conversely, adding of infliximab (IFX) to the culture medium inhibited this upregulation significantly. In conclusion, single-dose TAA administration induces a sequence of events with a defined upregulation of gene expression of inflammatory chemokines and cytokines and a transient accumulation of NGs within the portal area and macrophages along the sinusoids throughout the liver. Periportal inflammation seems to precede hepatocellular damage.

Exogenous rhTRX reduces lipid accumulation under LPS-induced inflammation

Redox-regulating molecule, recombinant human thioredoxin (rhTRX) which shows anti-inflammatory, and anti-oxidative effects against lipopolysaccharide (LPS)-stimulated inflammation and regulate protein expression levels. LPS-induced reactive oxygen intermediates (ROI) and NO production were inhibited by exogenous rhTRX. We identified up/downregulated intracellular proteins under the LPS-treated condition in exogenous rhTRX-treated A375 cells compared with non-LPS-treated cells via 2-DE proteomic analysis. Also, we quantitatively measured cytokines of in vivo mouse inflammation models using cytometry bead array. Exogenous rhTRX inhibited LPS-stimulated production of ROI and NO levels. TIP47 and ATP synthase may influence the inflammation-related lipid accumulation by affecting lipid metabolism. The modulation of skin redox environments during inflammation is most likely to prevent alterations in lipid metabolism through upregulation of TIP47 and ATP synthase and downregulation of inflammatory cytokines. Our results demonstrate that exogenous rhTRX has anti-inflammatory properties and intracellular regulatory activity in vivo and in vitro. Monitoring of LPS-stimulated pro-inflammatory conditions treated with rhTRX in A375 cells could be useful for diagnosis and follow-up of inflammation reduction related with candidate proteins. These results have a therapeutic role in skin inflammation therapy.

The vagal innervation of the gut and immune homeostasis

The central nervous system interacts dynamically with the immune system to modulate inflammation through humoral and neural pathways. Recently, in animal models of sepsis, the vagus nerve (VN) has been proposed to play a crucial role in the regulation of the immune response, also referred to as the cholinergic anti-inflammatory pathway. The VN, through release of acetylcholine, dampens immune cell activation by interacting with α-7 nicotinic acetylcholine receptors. Recent evidence suggests that the vagal innervation of the gastrointestinal tract also plays a major role controlling intestinal immune activation. Indeed, VN electrical stimulation potently reduces intestinal inflammation restoring intestinal homeostasis, whereas vagotomy has the reverse effect. In this review, we will discuss the current understanding concerning the mechanisms and effects involved in the cholinergic anti-inflammatory pathway in the gastrointestinal tract. Deeper investigation on this counter-regulatory neuroimmune mechanism will provide new insights in the cross-talk between the nervous and immune system leading to the identification of new therapeutic targets to treat intestinal immune disease.

The novel guanylhydrazone CPSI-2364 ameliorates ischemia reperfusion injury after experimental small bowel transplantation

BACKGROUND

Resident macrophages within the tunica muscularis are known to play a crucial role in initiating severe inflammation in response to ischemia reperfusion injury after intestinal transplantation contributing to graft dysmotility, bacterial translocation, and possibly, acute rejection. The p38 mitogen-activated protein kinase is a key player in the signaling of proinflammatory cytokine synthesis in macrophages. Therefore, we investigated the effects of CPSI-2364, an apparent macrophage-specific inhibitor of the p38 mitogen-activated protein kinase pathway in an isogenic intestinal rat transplantation model.

METHODS

Recipient and donor animals were treated perioperatively with CPSI-2364 (1 mg/kg, intravenously) or vehicle solution. Nontransplanted animals served as control. Animals were killed 30 min, 3 hr, and 18 hr after reperfusion.

RESULTS

CPSI-2364 treatment resulted in significantly less leukocyte infiltration and significantly improved graft motor function (18 hr). Messenger RNA expression of proinflammatory cytokines (interleukin 6) and kinetic active mediators (NO) was reduced by CPSI-2364 in the early phase after transplantation. Histologic evaluation revealed the protective effects of CPSI-2364 treatment by a significantly less destruction of mucosal integrity at all time points. Perioperative treatment with CPSI-2364 improves graft motor function through impaired inflammatory responses to ischemia reperfusion injury by inhibition of proinflammatory cytokines and suppression of nitric oxide production in macrophages.

CONCLUSIONS

CPSI-2364 presents as a promising complementary pharmacological approach preventing postoperative dysmotility for clinical intestinal transplantation.

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

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

The clinical importance of the anti-inflammatory vagovagal reflex

Excessive activation of the immune system is prevented by anti-inflammatory mediators such as corticosteroids and anti-inflammatory cytokines. Recently, it became clear that the brain not only senses peripheral inflammation through vagal afferent nerve fibers, but also provides an integrated response dampening the immune system through vagal efferents. This so-called anti-inflammatory pathway has been introduced as a third system by which the immune system is modulated. In sepsis, the anti-inflammatory effect is mediated by modulation of splenic macrophages, whereas in the gut, vagal nerve fibers synapse with enteric cholinergic neurons interacting with resident intestinal macrophages. In this chapter, the preclinical data underscoring the importance of this pathway are summarized, and its clinical significance is reviewed. Finally, the current data supporting its relevance to human disease and its therapeutic potential will be discussed. Insight in the mechanisms underlying these crucial properties will lead to better understanding of immune-mediated diseases and ultimately to improved anti-inflammatory therapies.

Role of interleukin-6 in hemopoietic and non-hemopoietic synergy mediating TLR4-triggered late murine ileus and endotoxic shock

BACKGROUND

Early murine endotoxin-induced ileus at 6 h is exclusively mediated by non-hemopoietic TLR4/MyD88 signaling despite molecular activation of hemopoietic cells which included a significant IL-6 mRNA induction. Our objective was to define the role of hemopoietic cells in LPS/TLR4-triggered ileus and inflammation over time, and identify mechanisms of ileus.

METHODS

CSF-1(-/-) , TLR4 non-chimera and TLR4 chimera mice were single-shot intraperitoneal injected with ultrapure lipopolysaccharide (UP-LPS) and studied up to 4 days. Subgroups of TLR4(WT) mice were additionally intravenously injected with exogenous recombinant IL-6 (rmIL-6) or murine soluble IL-6 receptor blocking antibody (anti-sIL-6R mAB).

KEY RESULTS

Hemopoietic TLR4 signaling independently mediated UP-LPS-induced ileus at 24 h, but chemotactic muscularis neutrophil extravasation was not causatively involved and mice lacking CSF-1-dependent macrophages died prematurely. Synergy of hemopoietic and non-hemopoietic cells determined ileus severity and mortality which correlated with synergistic cell lineage specific transcription of inflammatory mediators like IL-6 within the intestinal muscularis. Circulating IL-6 levels were LPS dose dependent, but exogenous rmIL-6 did not spark off a self-perpetuating inflammatory response triggering ileus. Sustained therapeutic inhibition of functional IL-6 signaling efficiently ameliorated late ileus while preemptive antibody-mediated IL-6R blockade was marginally effective in mitigating ileus. However, IL-6R blockade did not prevent endotoxin-associated mortality nor did it alter circulating IL-6 levels.

CONCLUSIONS & INFERENCES

A time-delayed bone marrow-driven mechanism of murine endotoxin-induced ileus exists, and hemopoietic cells synergize with non-hemopoietic cells thereby prolonging ileus and fueling intestinal inflammation. Importantly, IL-6 signaling via IL-6R/gp130 drives late ileus, yet it did not regulate mortality in endotoxic shock.

Iatrogenic extracellular matrix disruption as a local trigger for postoperative ileus

BACKGROUND

Active matrix metallopeptidase 9 (MMP-9) disruption of the extracellular matrix (ECM) plays an important role in inflammatory disorders. In this study, we investigated the inflammatory role of MMP-9 and the ECM breakdown product hyaluronan as a trigger for the postoperative intestinal inflammatory response of postoperative ileus.

METHODS

We performed a standardized intestinal surgical manipulation on rats to produce ileus assessed by the oral non-digestible fluorescein isothiocyanate-dextran transit assay. We studied isolated intestinal muscularis extracts for mRNA expressions of interleukin 6 (IL-6), MMP-9 and CD44. We quantified peritoneal MMP-9 activity using zymography, and quantified peritoneal fluid and serum for hyaluronan and tissue inhibitor of metalloproteinase 1 levels by enzyme-linked immunosorbent assay (ELISA). We cultured peritoneal macrophages and exposed them to peritoneal fluid or synthetic hyaluronan for ELISA analysis of IL-6 and macrophage inflammatory protein-1α.

RESULTS

Transit was significantly delayed after surgical manipulation, and extracts of the isolated jejunal and colonic muscularis demonstrated a significant induction of IL-6, MMP-9, and CD44 mRNAs compared with controls. Zymography confirmed significant MMP-9 activity in peritoneal fluid compared with controls. Enzyme-linked immunosorbent assay measurements showed a significant up-regulation in hyaluronan and tissue inhibitor of metalloproteinase 1 in the peritoneal fluid and serum. In addition, ELISA and reverse transcriptase-polymerase chain reaction measurements of peritoneal macrophages stimulated with postsurgical peritoneal fluid and synthetic hyaluronan resulted in higher expressions of IL-6 and macrophage inflammatory protein-1α in the macrophage supernatant.

CONCLUSIONS

Our results confirm that MMP-9 disruption in the ECM with hyaluronan release and muscularis CD44 receptor induction has the potential to trigger muscularis proinflammatory cascades that cause postoperative ileus. Matrix metallopeptidase 9 inhibition may be a novel therapeutic approach to limit postoperative ileus.

Proinflammatory chemokines in the intestinal lumen contribute to intestinal dysfunction during endotoxemia

Intestinal failure is common in patients with septic shock, with dysfunction of the gut often manifesting as both a cause and consequence of their critical illness. Most studies investigating the pathogenesis of intestinal failure focus on the systemic aspect, although few data examine the inflammatory signaling in the intestinal lumen. Having previously demonstrated apical/luminal chemokine secretion in an in vitro model of intestinal inflammation, we hypothesized that endotoxemia would induce secretion of proinflammatory chemokines into the intestinal lumen. In addition, we examined the contribution of these mediators to intestinal dysmotility. C57/BL6 male mice were injected intraperitoneally with LPS. Serum, intestinal tissue, and intestinal luminal contents were harvested for cytokine analysis. For intestinal motility studies, a transit assay was performed after oral gavage of chemokines. Caco-2 cells grown on Transwell culture inserts were used to examine the role of the intestinal epithelium in chemokine secretion. Monocyte chemoattractant protein 1 (MCP-1/CCL2) and macrophage-derived chemokine (MDC/CCL22) were secreted into the lumen of multiple segments of the gut during endotoxemia in mice. In vitro work showed that the intestinal epithelium participates in monocyte chemoattractant protein 1 and MDC secretion and expresses the CCR2 and CCR4 receptors for these chemokines. Intestinal transit studies show that oral gavage of MDC results in impaired gut motility. This study demonstrates that the intestinal lumen is an active compartment in the gut's inflammatory response. Proinflammatory chemokines are secreted into the intestinal lumen during endotoxemia. These intraluminal chemokines contribute to intestinal dysmotility, complicating intestinal failure.

Differential molecular and cellular immune mechanisms of postoperative and LPS-induced ileus in mice and rats

Ileus is caused by the initiation of a complex cascade of molecular and cellular inflammatory responses within the intestinal muscularis, which might be species specific. Our objective was to investigate a possible immunological divergence in the mechanisms of postoperative- and endotoxin-induced ileus in C57BL/6 mice and Sprague-Dawley rats. Gastrointestinal transit (GIT) was measured at 24 h after the injurious stimulus. MPO-staining and F4/80 immunohistochemistry were used to quantify polymorphonuclear and monocyte infiltration of jejunal muscularis whole-mounts, and intestinal muscularis MCP-1, ICAM-1 and iNOS gene expression was assessed by RT-PCR. Intestinal muscularis subjected to in vivo surgical manipulation (SM) or LPS treatment was cultured for 24 h, and the liberation of nitric oxide and chemokines/cytokines into the culture medium was analyzed by Griess reaction and Luminex multiplex assay. Intestinal SM and lipopolysaccharide (LPS) (15 mg/kg) caused a significant delay in gastrointestinal transit, which was more severe in mice compared to rats in both injury models. Both SM- and LPS-triggered neutrophil and monocytic extravasation into the rat jejunal muscularis exceeded the cellular infiltration seen in mice. These results correlated with significantly greater increases in rat muscularis MCP-1 (syn. CCL2), ICAM-1 and iNOS message with more subsequent NO production after SM or LPS compared to mouse. The cultured muscularis obtained from SM mice released significantly more inflammatory proteins such as TNF-α, IL-1-α, IL-4 and GM-CSF compared to the manipulated rat muscularis. In contrast, LPS initiated the secretion of significantly more IL-1β by the inflamed rat muscularis compared to the mouse, but GM-CSF (syn. CSF2) liberation from mouse muscularis was markedly higher compared to LPS-treated rat muscularis. The data indicate that mechanistically the development of ileus in rat is mediated predominately through a leukocytic pathway consisting of chemotaxis, cellular extravasation and NO liberation. Whereas, the more intense mouse ileus evolves via a potent but injury-specific local cytokine response.

Intravital microscopy of the murine urinary bladder microcirculation

OBJECTIVE

To establish an in vivo mouse model of the urinary bladder microcirculation, and characterize the molecular mechanisms of endotoxin-induced leukocyte recruitment.

METHODS

The murine model was adapted from a technique previously reported for the rat. Mouse bladder microcirculation was observed using intravital microscopy, four hours after intravesical challenge with lipopolysaccharide (LPS) and leukocyte-endothelial interactions were examined. Molecular mechanisms of leukocyte recruitment were identified using antibodies to adhesion molecules and chemokines.

RESULTS

LPS from Escherichia coli administered intravesically resulted in a significant increase in leukocyte adhesion and rolling at four hours post stimulation. LPS from Pseudomonas aeruginosa administered at similar doses resulted in a significant, but lower increase in leukocyte adhesion after four hours compared with E. coli LPS. Leukocyte adhesion within the bladder microcirculation was dependent on α(4) -integrins and ICAM-1, whereas leukocyte rolling was P-selectin dependent, but α(4) -integrin independent. Blockade of MIP-2 and KC did not alter leukocyte-endothelial interactions. The bladder endothelium expressed P-selectin, ICAM-1, VCAM-1, MIP-2, and MCP-1. Only VCAM-1 endothelial expression was significantly increased after LPS stimulation.

CONCLUSION

The mouse model of the urinary bladder microcirculation is suitable for the study of inflammatory responses during urinary tract infection (UTI) in vivo.

Combination therapy of tacrolimus and infliximab reduces inflammatory response and dysmotility in experimental small bowel transplantation in rats

BACKGROUND

Intestinal transplantation initiates a functionally relevant inflammatory response by activation of resident macrophages within the muscularis associated with dysmotility. Infliximab is used successfully as a potent anti-inflammatory agent for the treatment of chronic inflammatory bowel diseases and as rescue therapy in acute steroid-resistant rejection in selected settings in clinical small bowel transplantation. We hypothesize that additional perioperative treatment with infliximab diminishes initiation of the inflammatory cascade and improves motility in small bowel grafts using a standard tacrolimus immunosuppressive protocol.

METHODS

Orthotopic intestinal transplantation was performed in rats. In two treatment groups (24/168 hr), infliximab was administered intravenously directly after reperfusion and tacrolimus was injected intramuscularly after transplantation and once a day. Two other treatment groups (24/168 hr) received standard immunosuppressive therapy with tacrolimus. Isogenic and allogenic transplanted vehicle-treated animals (24/168 hr) and native gut served as control.

RESULTS

Infliximab-treated grafts exhibited significantly less leukocyte infiltration at 24/168 hr after transplantation and at 168 hr significantly less apoptosis in the tunica muscularis compared with tacrolimus monotherapy. Additional infliximab treatment resulted in increased smooth muscle contractility (30%) after 24 hr compared with tacrolimus control.

CONCLUSIONS

Dysmotility of transplanted small bowel results from reperfusion injury and acute rejection. Additional perioperative treatment with infliximab reduces early unspecific inflammatory responses and complements immunosuppressive therapy with tacrolimus.

Inflammatory response in multiple organs in a mouse model of acute alcohol intoxication and burn injury

This study characterized the inflammatory response after burn injury and determined whether ethanol (EtOH) intoxication at the time of burn injury influences this response. To accomplish this, male mice were gavaged with EtOH (2.9 g/kg) 4 hours before 12 to 15% TBSA sham or burn injury. Mice were killed on day 1 after injury; blood, small intestine, lung, and liver were collected to measure interleukin (IL)-6, IL-10, IL-18, and Monocyte chemotactic protein-1 (MCP-1) levels. In addition, neutrophil infiltration, myeloperoxidase activity, and edema formation were also measured in the small intestine, lung, and liver. There was no difference in the inflammatory markers in the small intestine, lung, and liver in mice receiving either sham or burn injury alone except IL-6 that was increased in all four tissue compartments after burn injury alone. However, when compared with EtOH or burn injury alone, EtOH combined with burn injury resulted in a significant increase in cytokines, neutrophil infiltration, myeloperoxidase activity, and edema in the small intestine, liver, and lung tissue. Furthermore, a significant increase in IL-6 and MCP-1 was observed in circulation after EtOH intoxication and burn injury compared with either EtOH intoxication or burn injury alone; no other cytokines were detected in circulation. These findings suggest that acute EtOH intoxication exacerbates the inflammatory response after burn injury.

Colonic anastomotic healing in the context of altered macrophage function and endotoxemia

PURPOSE

Prevention of perioperative activation of intestinal muscularis macrophages is a promising intervention to avoid post-traumatic gastrointestinal tract dysfunction. However, impaired macrophage function could have deleterious consequences on anastomotic healing, especially in complications aggravating the healing process itself, such as infectious problems either as preexisting local inflammation or infection (e.g., complicated diverticulitis) or endotoxemia due to early postoperative infections (e.g., pneumonia). Aim of this study was to investigate colonic anastomotic healing in macrophage-depleted mice in the presence of endotoxemia.

METHODS

Colonic anastomoses were performed, and mice were randomized into six groups (wild type; wild type with endotoxemia; pharmacological depletion of macrophages; pharmacological depletion with endotoxemia; genetically conditioned within the gut muscularis macrophage-deficient osteopetrotic mice; osteopetrotic mice with endotoxemia). Anastomotic tissues were removed 2, 5, and 10 days after surgery and used for functional, histological, biochemical, and molecular investigations.

RESULTS

After pharmacological pretreatment, an almost complete depletion of macrophages was found in the muscularis up to 24 h postoperatively. Bursting pressure was significantly lower than 10 days after anastomotic procedure in osteopetrotic mice during endotoxemia, in marked contrast to transient pharmacologically macrophage-depleted mice. Pharmacological depletion during endotoxemia did not affect hydroxyproline concentration. Finally, in osteopetrotic mice during endotoxemia, collagen-3 expression was significantly lower compared to controls.

CONCLUSIONS

In our current model, we demonstrate that perioperative pharmacological macrophage depletion and inactivation transiently diminishes muscularis macrophages and does not affect intestinal anastomotic healing in the presence of endotoxemia. However, a long-lasting macrophage absence or dysfunction impairs anastomotic healing and could be a risk factor for postoperative anastomotic leakage.

Impact of CCR7 on the gastrointestinal field effect

Standardized intestinal manipulation (IM) leads to local bowel wall inflammation subsequently spreading over the entire gastrointestinal tract. Previously, we demonstrated that this so-called gastrointestinal field effect (FE) is immune mediated. This study aimed to investigate the role of CCR7 in IM-induced FE. Since CCR7 is expressed on activated dendritic cells and T cells and is well known to control their migration, we hypothesized that lack of CCR7 reduces or abolishes FE. Small bowel muscularis and colonic muscularis from CCR7(-/-) and wild-type (WT) mice were obtained after IM of the jejunum or sham operation. FE was analyzed by measuring gastrointestinal transit time of orally given fluorescent dextran (geometric center), colonic transit time, infiltration of MPO-positive cells, and circular smooth muscle contractility. Furthermore, mRNA levels of the inflammatory cytokine IL-6 were determined by RT-PCR. The number of dendritic cells and CD3+CD25+ T cells separately isolated from jejunum and colon was determined in mice after IM and sham operation. There was no significant difference in IL-6 mRNA upregulation in colonic muscularis between sham-operated WT and CCR7(-/-) mice after IM. Contractility of circular muscularis strips of the colon was significantly improved in CCR7(-/-) animals following IM and did not vary significantly from sham-operated animals. Additionally, inflammation of the colon determined by the number of MPO-positive cells and colonic transit time was significantly reduced in CCR7(-/-) mice. In contrast, jejunal contractility and jejunal inflammation of transgenic mice did not differ significantly from WT mice after IM. These data are supported by a significant increase of CD3+CD25+ T cells in the colonic muscularis of WT mice after IM, which could not be observed in CCR7(-/-) mice. These data demonstrate that CCR7 is required for FE and postoperative ileus. CCR7 indirectly affects FE by inhibiting migration of activated dendritic cells and of T cells from the jejunum to the colon. These findings support the critical role of the adaptive immune system in FE.

Interplay between inflammation, immune system and neuronal pathways: Effect on gastrointestinal motility

Sepsis is a systemic inflammatory response representing the leading cause of death in critically ill patients, mostly due to multiple organ failure. The gastrointestinal tract plays a pivotal role in the pathogenesis of sepsis-induced multiple organ failure through intestinal barrier dysfunction, bacterial translocation and ileus. In this review we address the role of the gastrointestinal tract, the mediators, cell types and transduction pathways involved, based on experimental data obtained from models of inflammation-induced ileus and (preliminary) clinical data. The complex interplay within the gastrointestinal wall between mast cells, residential macrophages and glial cells on the one hand, and neurons and smooth muscle cells on the other hand, involves intracellular signaling pathways, Toll-like receptors and a plethora of neuroactive substances such as nitric oxide, prostaglandins, cytokines, chemokines, growth factors, tryptases and hormones. Multidirectional signaling between the different components in the gastrointestinal wall, the spinal cord and central nervous system impacts inflammation and its consequences. We propose that novel therapeutic strategies should target inflammation on the one hand and gastrointestinal motility, gastrointestinal sensitivity and even pain signaling on the other hand, for instance by impeding afferent neuronal signaling, by activation of the vagal anti-inflammatory pathway or by the use of pharmacological agents such as ghrelin and ghrelin agonists or drugs interfering with the endocannabinoid system.

Influence of immunosuppression on alloresponse, inflammation and contractile function of graft after intestinal transplantation

In small bowel transplantation (SBTx), graft manipulation, ischemia/reperfusion injury and acute rejection initiate a severe cellular and molecular inflammatory response in the muscularis propria leading to impaired motility of the graft. This study examined and compared the effect of tacrolimus and sirolimus on inflammation in graft muscularis. After allogeneic orthotopic SBTx, recipient rats were treated with tacrolimus or sirolimus. Tacrolimus and sirolimus attenuated neutrophilic, macrophage and T-cell infiltration in graft muscularis, which was associated with reduced apoptotic cell death. Nonspecific inflammatory mediators (IL-6, MCP-1) and T-cell activation markers (IL-2, IFN-gamma) were highly upregulated in allogeneic control graft muscularis 24 h and 7 days after SBTx, and tacrolimus and sirolimus significantly suppressed upregulation of these mediators. In vitro organ bath method demonstrated a severe decrease in graft smooth muscle contractility in allogeneic control (22% of normal control). Correlating with attenuated upregulation of iNOS, tacrolimus and sirolimus treatment significantly improved contractility (64% and 72%, respectively). Although sirolimus reduced cellular and molecular inflammatory response more efficiently after 24 h, contrary tacrolimus prevented acute rejection more efficiently. In conclusion, tacrolimus and sirolimus attenuate cellular and molecular inflammatory response in graft muscularis and subsequent dysmotility of the graft after allogeneic SBTx.

Membrane TLR signaling mechanisms in the gastrointestinal tract during sepsis

Our bacterial residents are deadly Janus-faced indwellers that can lead to a sepsis-induced systemic inflammatory response syndrome and multiple organ failure. Over half of ICU patients suffer from infections and sepsis remains one of the top 10 causes of death worldwide. Severe ileus frequently accompanies sepsis setting up an insidious cycle of gut-derived microbial translocation and the copious intestinal production of potent systemic inflammatory mediators. Few therapeutic advances have occurred to prevent/treat the sequelae of sepsis. Here, we selectively review studies on cellular membrane-bound Toll-like receptor (TLR) mechanisms of ileus. Virtually, no data exist on Gram-positive/TLR2 signaling mechanisms of ileus; however, TLR2 is highly inducible by numerous inflammatory mediators and studies using clinically relevant scenarios of Gram-positive sepsis are needed. Specific Gram-negative/TLR4 signaling pathways are being elucidated using a 'reverse engineering' approach, which has revealed that endotoxin-induced ileus is dually mediated by classical leukocyte signaling and by a MyD88-dependent non-bone marrow-derived mechanism, but the specific roles of individual cell populations are still unknown. Like TLR2, little is also know of the role of flagellin/TLR5 signaling in ileus. But, much can be learned by understanding TLR signaling in other systems. Clearly, the use of polymicrobial models provides important clinical relevancy, but the simultaneous activation of virtually all pattern recognition receptors makes it impossible to discretely study specific pathways. We believe that the dissection of individual TLR pathways within the gastrointestinal tract, which can then be intelligently reassembled in a meaningful manner, will provide insight into treatments for sepsis.

Single-dose gamma-irradiation induces up-regulation of chemokine gene expression and recruitment of granulocytes into the portal area but not into other regions of rat hepatic tissue

Liver damage is a serious clinical complication of gamma-irradiation. We therefore exposed rats to single-dose gamma-irradiation (25 Gy) that was focused on the liver. Three to six hours after irradiation, an increased number of neutrophils (but not mononuclear phagocytes) was observed by immunohistochemistry to be attached to portal vessels between and around the portal (myo)fibroblasts (smooth muscle actin and Thy-1(+) cells). MCP-1/CCL2 staining was also detected in the portal vessel walls, including some cells of the portal area. CC-chemokine (MCP-1/CCL2 and MCP-3/CCL7) and CXC-chemokine (KC/CXCL1, MIP-2/CXCL2, and LIX/CXCL5) gene expression was significantly induced in total RNA from irradiated livers. In laser capture microdissected samples, an early (1 to 3 hours) up-regulation of CCL2, CXCL1, CXCL8, and CXCR2 gene expression was detected in the portal area but not in the parenchyma; with the exception of CXCL1 gene expression. In addition, treatment with an antibody against MCP-1/CCL2 before irradiation led to an increase in gene expression of interferon-gamma and IP-10/CXCL10 in liver tissue without influencing the recruitment of granulocytes. Indeed, the CCL2, CXCL1, CXCL2, and CXCL5 genes were strongly expressed and further up-regulated in liver (myo)fibroblasts after irradiation (8 Gy). Taken together, these results suggest that gamma-irradiation of the liver induces a transient accumulation of granulocytes within the portal area and that (myo)fibroblasts of the portal vessels may be one of the major sources of the chemokines involved in neutrophil recruitment. Moreover, inhibition of more than one chemokine (eg, CXCL1 and CXCL8) may be necessary to reduce leukocytes recruitment.