In mice, a subpopulation of gut dendritic cells (DCs) expressing CD103 drives the development of regulatory T (T(reg)) cells. Further, it was recently described that the cross-talk between human ...intestinal epithelial cells (IECs) and DCs helps in maintaining gut immune homeostasis via the induction of non-inflammatory DCs. In this study, an analysis was carried out to determine whether IECs could promote the differentiation of CD103+ tolerogenic DCs, and the function of primary CD103+ DCs isolated from human mesenteric lymph nodes (MLNs) was evaluated.
Monocyte-derived DCs (MoDCs) and circulating CD1c+ DCs were conditioned or not with supernatants from Caco-2 cells or IECs isolated from healthy donors or donors with Crohn's disease and analysed for their ability to induce T(reg) cell differentiation. In some cases, transforming growth factor beta (TGFbeta), retinoic acid (RA) or thymic stromal lymphopoietin (TSLP) were neutralised before conditioning. CD103+ and CD103- DCs were sorted by fluorescence-activated cell sorting (FACS) from MLNs and used in T(reg) cell differentiation experiments.
It was found that human IECs promoted the differentiation of tolerogenic DCs able to drive the development of adaptive Foxp3+ T(reg) cells. This control was lost in patients with Crohn's disease and paralleled a reduced expression of tolerogenic factors by primary IECs. MoDCs differentiated with RA or IEC supernatant upregulated the expression of CD103. Consistently, human primary CD103+ DCs isolated from MLNs were endowed with the ability to drive T(reg) cell differentiation. This subset of DCs expressed CCR7 and probably represents a lamina propria-derived migratory population.
A population of tolerogenic CD103+ DCs was identified in the human gut that probably differentiate in response to IEC-derived factors and drive T(reg) cell development.
Background
Electrical stimulation of the cervical vagus nerve (VNS) prevents postoperative ileus (POI) in mice. As this approach requires an additional cervical procedure, we explored the possibility ...of peroperative abdominal VNS in mice and human.
Methods
The effect of cervical and abdominal VNS was studied in a murine model of POI and lipopolysaccharide (LPS)‐induced sepsis. Postoperative ileus was quantified by assessment of intestinal transit of fluorescent dextran expressed as geometric center (GC). Next, the effect of cervical and abdominal VNS on heart rate was determined in eight Landrace pigs to select the optimal electrode for VNS in human. Finally, the effect of sham or abdominal VNS on LPS‐induced cytokine production of whole blood was studied in patients undergoing colorectal surgery.
Key Results
Similar to cervical VNS, abdominal VNS significantly decreased LPS‐induced serum tumor necrosis factor‐α (TNFα) levels (abdominal VNS: 366±33 pg/mL vs sham: 822±105 pg/mL; P<.01). In line, in a murine model of POI, abdominal VNS significantly improved intestinal transit (GC: sham 5.1±0.2 vs abdominal VNS: 7.8±0.6; P<.01) and reduced intestinal inflammation (abdominal VNS: 35±7 vs sham: 80±8 myeloperoxidase positive cells/field; P<.05). In pigs, heart rate was reduced by cervical VNS but not by abdominal VNS. In humans, abdominal VNS significantly reduced LPS‐induced IL8 and IL6 production by whole blood.
Conclusions & Inferences
Abdominal VNS is feasible and safe in humans and has anti‐inflammatory properties. As abdominal VNS improves POI similar to cervical VNS in mice, our data indicate that peroperative abdominal VNS may represent a novel approach to shorten POI in man.
Vagus nerve stimulation (VNS) has anti‐inflammatory effects in immune‐mediated disorders such as sepsis and postoperative ileus. Traditionally, VNS has always been performed at cervical level. In this article, we evaluated the anti‐inflammatory properties of abdominal VNS in sepsis and postoperative ileus, thus avoiding additional incisions in the neck.
CD103(+) gut dendritic cells (DCs) have been shown to be required for de novo conversion of adaptive T regulatory (Treg) cells. Indoleamine 2,3-dioxygenase (IDO) is an enzyme involved in tryptophan ...catabolism that is expressed by DCs isolated from tumour-draining lymph nodes. IDO-expressing DCs sustain and differentiate Tregs. The aim of this study was to investigate the expression and the possible physiological role of IDO in the tolerogenic properties of intestinal DCs.
The expression level of IDO in CD103(+) and CD103(-) DCs was analysed by qRT-PCR, western blot and immunofluorescence. CD103(+) and CD103(-) DCs were sorted from mesenteric lymph nodes (MLNs) and the small intestinal lamina propria, and the role of IDO in the conversion of Tregs and Th effector cell development was evaluated via specific inhibition or gene deletion. Oral tolerance, experimental colitis and T cell differentiation in vivo were assessed upon IDO inactivation.
We show that, primarily, CD103(+) but not CD103(-) gut DCs express IDO whose inhibition results in reduced CD4(+)Foxp3(+) T regulatory cell conversion and enhanced T cell proliferation. When IDO was inhibited or genetically deleted there was an increase in Th1 and Th17 differentiation both in vitro and in vivo. Finally, in vivo IDO blockade affected the development of Tregs specific for orally administered antigens, impaired oral tolerance induction and exacerbated colitis.
We identified a new IDO-dependent pathway leading to acquisition of tolerogenic functions in mucosal CD103-expressing DCs, indicating IDO as a possible therapeutic target for gut disorders.
Intestinal dendritic cells (DCs) have been shown to display specialized functions, including the ability to promote gut tropism to lymphocytes, to polarize noninflammatory responses, and to drive the ...differentiation of adaptive Foxp3(+) regulatory T (T(reg)) cells. However, very little is known about what drives the mucosal phenotype of DCs. Here, we present evidence that the local microenvironment, and in particular intestinal epithelial cells (ECs), drive the differentiation of T(reg)-cell-promoting DCs, which counteracts Th1 and Th17 development. EC-derived transforming growth factor-beta (TGF-beta) and retinoic acid (RA), but not thymic stromal lymphopoietin (TSLP), were found to be required for DC conversion. After EC contact, DCs upregulated CD103 and acquired a tolerogenic phenotype. EC-conditioned DCs were capable of inducing de novo T(reg) cells with gut-homing properties that when adoptively transferred, protected mice from experimental colitis. Thus, we have uncovered an essential mechanism in which EC control of DC function is required for tolerance induction.
Background
Postoperative ileus (POI) is characterized by a transient inhibition of gastrointestinal (GI) motility after abdominal surgery mediated by the inflammation of the muscularis externa (ME). ...The aim of this study was to identify alterations in the enteric nervous system that may contribute to the pathogenesis of POI.
Methods
Gastrointestinal transit, contractility of isolated smooth muscle strips and inflammatory parameters were evaluated at different time points (1.5 h to 10 days) after intestinal manipulation (IM) in mice. Immune‐labeling was used to visualize changes in myenteric neurons.
Key Results
Intestinal manipulation resulted in an immediate inhibition of GI transit recovering between 24 h and 5 days. In vitro contractility to K+ (60 mM) or carbachol (10−9 to 10−4 M) was biphasically suppressed over 24 h after IM (with transient recovery at 6 h). The first phase of impaired myogenic contractility was associated with increased expression of TNF‐α, IL‐6 and IL‐1α. After 24 h, we identified a significant reduction in electrical field stimulation‐evoked contractions and relaxations, lasting up to 10 days after IM. This was associated with a reduced expression of chat and nos1 genes.
Conclusions & Inferences
Intestinal manipulation induces two waves of smooth muscle inhibition, most likely mediated by inflammatory cytokines, lasting up to 3 days after IM. Further, we here identify a late third phase (>24 h) characterized by impaired cholinergic and nitrergic neurotransmission persisting after recovery of muscle contractility. These findings illustrate that POI results from inflammation‐mediated impaired smooth muscle contraction, but also involves a long‐lasting impact of IM on the enteric nervous system.
We aimed to identify alterations in the enteric nervous system that may contribute to the pathogenesis of postoperative ileus. Surgical manipulation of the intestine induced two phases of muscle dysfunction over 24 h and a late prolonged phase of impaired neurotransmission. Our data show that intestinal surgery affect both muscle cells and neurons and different inflammatory mechanisms underlie the different phases.
Injury to the enteric nervous system (ENS) can cause several gastrointestinal (GI) disorders including achalasia, irritable bowel syndrome, and gastroparesis. Recently, a subpopulation of enteric ...glial cells with neuronal stem/progenitor properties (ENSCs) has been identified in the adult ENS. ENSCs have the ability of reconstituting the enteric neuronal pool after damage of the myenteric plexus. Since the estrogen receptor β (ERβ) is expressed in enteric glial cells and neurons, we investigated whether a selective ERβ agonist, LY3201, can influence neuronal and glial cell differentiation. Myenteric ganglia from the murine muscularis externa were isolated and cultured in either glial cell medium or neuronal medium. In glial cell medium, the number of glial progenitor cells (Sox10⁺) was increased by fourfold in the presence of LY3201. In the neuronal medium supplemented with an antimitotic agent to block glial cell proliferation, LY3201 elicited a 2.7-fold increase in the number of neurons (neurofilament⁺ or HuC/D⁺). In addition, the effect of LY3201 was evaluated in vivo in two murine models of enteric neuronal damage and loss, namely, high-fat diet and topical application of the cationic detergent benzalkonium chloride (BAC) on the intestinal serosa, respectively. In both models, treatment with LY3201 significantly increased the recovery of neurons after damage. Thus, LY3201 was able to stimulate glial-to-neuron cell differentiation in vitro and promoted neurogenesis in the damaged myenteric plexus in vivo. Overall, our study suggests that selective ERβ agonists may represent a therapeutic tool to treat patients suffering from GI disorders, caused by excessive neuronal/glial cell damage.
Background
The orexigenic peptide ghrelin has anti‐inflammatory properties in colitis, however, the mechanism of action and the immune cells targeted remain still to be elucidated. Here, we assessed ...the possible effect of ghrelin on T helper (Th) cells in a T cell transfer model of chronic colitis.
Methods
Disease was induced in the recombination activating gene 1 knockout mice (Rag1−/−) by adoptive transfer of naïve Th cells from ghrelin receptor knockout mice (GRLN‐R−/−) or littermate wild‐type (WT) mice. The course and severity of colitis was assessed by monitoring body weight, diarrhea score, histological analysis, gene expression, and flow cytometry analysis. The possible effects of ghrelin on Th cell proliferation, polarization, and apoptosis was examined in vitro.
Key Results
Our data showed that Rag1−/− mice injected with GRLN‐R−/− Th cells displayed increased severity of colitis compared to mice injected with WT Th cells. In addition, Rag1−/− mice injected with GRLN‐R−/− Th cells had significantly higher intestinal inflammation and increased accumulation of Th1 and Th17 cells in the colon. In vitro, ghrelin directly affected proliferation of Th cells and induced apoptosis whereas it did not influence Th cell polarization.
Conclusion & Inferences
Our observations suggest that ghrelin modulates Th effector cells in the gut controlling proliferation and inducing apoptosis. Our findings further support the use of ghrelin as a novel therapeutic option to treat intestinal inflammatory diseases.
The expression of the orexigenic hormone ghrelin and its receptor has been reported on various immune cells including T helper (Th) cells both in humans and rodents. Based on the above, and taking into account the large expression of ghrelin in the bowel mucosa, we hypothesized that this peptide may directly modulate intestinal Th cells during colonic inflammation. Hence, we used a well‐characterized model of Th cell‐induced chronic colitis that allowed us to study the influence of ghrelin receptor specifically on Th cells. In this study, we observed that the lack of ghrelin signaling in Th cells significantly worsens colitis with increased colonic inflammation. Our data revealed a specific immunomodulatory effect of ghrelin on Th cells, making the ghrelin receptor a suitable therapeutic candidate to treat chronic intestinal inflammatory diseases.
Background
The severity of postoperative ileus (POI) has been reported to result from decreased contractility of the muscularis inversely related to the number of infiltrating leukocytes. However, we ...previously observed that the severity of POI is independent of the number of infiltrating leukocytes, indicating that different mechanisms must be involved. Here, we hypothesize that the degree of tissue damage in response to intestinal handling determines the upregulation of local cytokine production and correlates with the severity of POI.
Methods
Intestinal transit, the inflammatory response, I‐FABP (marker for tissue damage) levels and brain activation were determined after different intensities of intestinal handling.
Key Results
Intense handling induced a more pronounced ileus compared with gentle intestinal manipulation (IM). No difference in leukocytic infiltrates in the handled and non‐handled parts of the gut was observed between the two intensities of intestinal handling. However, intense handling resulted in significantly more tissue damage and was accompanied by a systemic inflammation with increased plasma levels of pro‐inflammatory cytokines. In addition, intense but not gentle handling triggered enhanced c‐Fos expression in the nucleus of the solitary tract (NTS) and area postrema (AP). In patients, plasma levels of I‐FABP and inflammatory cytokines were significantly higher after open compared with laparoscopic surgery, and were associated with more severe POI.
Conclusions & Inferences
Not the influx of leukocytes, rather the manipulation‐induced damage and subsequent inflammatory response determine the severity of POI. The release of tissue damage mediators and pro‐inflammatory cytokines into the systemic circulation most likely contribute to the impaired motility of non‐manipulated intestine.
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