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PubMed2006

Differential activity of IL-12 and IL-23 in mucosal and systemic innate immune pathology.

The CD40-CD154 pathway is important in the pathogenesis of inflammatory bowel disease. Here we show that injection of an agonistic CD40 mAb to T and B cell-deficient mice was sufficient to induce a pathogenic systemic and intestinal innate inflammatory response that was functionally dependent on tumor necrosis factor-alpha and interferon-gamma as well as interleukin-12 p40 and interleukin-23 p40 secretion. CD40-induced colitis, but not wasting disease or serum proinflammatory cytokine production, depended on interleukin-23 p19 secretion, whereas interleukin-12 p35 secretion controlled wasting disease and serum cytokine production but not mucosal immunopathology. Intestinal inflammation was associated with IL-23 (p19) mRNA-producing intestinal dendritic cells and IL-17A mRNA within the intestine. Our experiments identified IL-23 as an effector cytokine within the innate intestinal immune system. The differential role of IL-23 in local but not systemic inflammation suggests that it may make a more specific target for the treatment of IBD.

Animals↗

PubMed2005

Experimental inflammation of the rat distal colon inhibits ion secretion in the proximal colon by affecting the enteric nervous system.

Intestinal inflammation causes hyporesponsiveness of the inflamed tissue to secretagogues but little is known about the behaviour of the areas proximal to the site of inflammation. We studied the responses of the proximal segment of the colon to carbachol, histamine, isobutylmethylxanthine (IBMX) and vasoactive intestinal peptide (VIP) in rats with trinitrobenzenesulphonic acid (TNBS)-induced, chronic inflammation of the distal colon. Macroscopic and biochemical analysis ruled out the presence of inflammation in the proximal colon. When mounted in Ussing chambers under voltage-clamp conditions, basal transport and conductance were not affected. However, the maximum response in the concentration/response curves (short-circuit current) for carbachol and histamine was reduced in TNBS-treated rats, without changes in the EC(50). This effect corresponded to reduced chloride secretion, as demonstrated by ion substitution experiments. The responses to IBMX and VIP were virtually unaffected. The inhibitory effect was abolished by pretreatment with the neural blockers tetrodotoxin and lidocaine but not indomethacin, suggesting that the enteric nervous system is responsible for the inhibition. In conclusion, chronic distal inflammation of the distal colon results in inhibition of calcium-dependent secretion in the proximal colon via a reduction of the contribution of the enteric nervous system.

1-Methyl-3-isobutylxanthine↗

PubMed1996

IL-4 down-regulates the responsiveness of human intraepithelial lymphocytes.

IL-4 is an important regulator of intestinal inflammation, yet little is known regarding its action on intestinal lymphocytes. Intestinal lymphocytes were isolated from jejunal mucosa of patients undergoing gastric bypass operations for morbid obesity. The impact of IL-4 was measured by its effects on proliferation using 3H-thymidine incorporation, IL-2 production using the CTLL assay, and IL-2 receptor generation using immunofluorescence. The production of IL-4 was measured by ELISA. IL-4 significantly inhibited the proliferation of intraepithelial lymphocytes (IEL) to a variety of stimuli as well as the development of lymphokine-activated killer (LAK) cells. In contrast, it had no effect on the proliferation of CD8+ T cells from peripheral blood. The inhibitory effect of IL-4 on IEL did not occur during activation, since IL-2 production and receptor expression were not altered. Rather, it occurred during cell cycling, since over 50% inhibition resulted whether IL-4 was added at the initiation of an IL-2-stimulated culture or after 24 or 48 h incubation. IL-4 was secreted by activated lamina propria lymphocytes (LPL) but not by IEL. IL-4, produced by activated LPL, may enter the epithelial compartment and down-regulate responsiveness of IEL.

Down-Regulation↗

PubMed2004

Decreased availability of intestinal dopamine in transmural colitis may relate to inhibitory effects of interferon-gamma upon L-DOPA uptake.

AIMS: The present study aimed to evaluate the relationship between intestinal inflammation, interferon-gamma (IFN-gamma) levels and intestinal levels of dopamine, its precursor l-3,4-dihydroxyphenylalanine (L-DOPA), and the activity of aromatic L-amino acid decarboxylase (AADC) activity along the digestive tract in a rat experimental model of colitis. METHODS: Colitis was induced by rectal administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS). Catechol derivatives were assayed by means of HPLC-EC. RESULTS: It is shown that dopamine and noradrenaline levels in the distal colon (inflamed mucosa), but not in the ileum (non-inflamed mucosa), of TNBS-treated rats were markedly lower than in control animals. A slight decrease in L-DOPA tissue levels, no changes in AADC activity and an increase in plasma IFN-gamma levels accompanied this decrease in dopamine levels. Exposure of Caco-2 cells, a human intestinal epithelial cell line, to human IFN-gamma resulted in a concentration-dependent and long-lasting inhibition of L-DOPA uptake, which most likely explains the decrease in dopamine levels in the inflamed mucosa. CONCLUSION: Changes in tissue levels of noradrenaline and dopamine in experimental colitis in the rat follow a similar pattern to that observed in patients with Crohn's disease and ulcerative colitis. In this model of experimental colitis, the decrease in dopamine levels is most likely explained by the inhibitory effect of IFN-gamma on L-DOPA uptake by intestinal epithelial cells.

Animals↗

PubMed1994

Technetium (99mTc)-labelled white cell scanning, 51Cr-EDTA and 14C-mannitol-labelled intestinal permeability studies: non-invasive methods of diagnosing acute intestinal graft-versus-host disease.

We describe a case of a 38-year-old female who presented with diarrhoea and abdominal pain 27 days after a second 'top-up' allogeneic marrow infusion for acute myeloid leukaemia (AML) in first remission. A clinical diagnosis of gut graft-versus-host disease (GVHD) was made. Technetium (99mTc)-labelled white cell scanning and intestinal permeability studies using 51Cr-EDTA and 14C-mannitol were undertaken to confirm the diagnosis. The 99mTc white cell scan showed extensive uptake in the small bowel and the urinary excretion of 51Cr-EDTA was increased, the results being consistent with intestinal inflammation and gut GVHD. 99mTc white cell scanning and intestinal permeability studies may assist in the diagnosis of gut GVHD and in assessing its extent and response to treatment.

Acute Disease↗

PubMed1998

Specific inhibition of plasma kallikrein modulates chronic granulomatous intestinal and systemic inflammation in genetically susceptible rats.

The kallikrein-kinin (K-K) (contact) system is activated during acute and chronic relapsing phases of enterocolitis induced in genetically susceptible Lewis rats by intramural injection of peptidoglycan-polysaccharide (PG-APS). Using the selective plasma kallikrein inhibitor P8720, we investigate whether activation of the K-K system plays a primary role in chronic granulomatous intestinal and systemic inflammation in this model. Group I (negative control) received human serum albumin intramurally. Group II (treatment) received PG-APS intramurally and P8720 orally. Group III (positive control) received PG-APS intramurally and albumin orally. P8720 attenuated the consumption of the contact proteins, high molecular weight kininogen (P<0.03), and factor XI (P<0.04) in group II vs. group III. P8720 decreased chronic intestinal inflammation measured by blinded gross (P<0.01) and histologic (P<0.0005) scores as well as systemic complications (arthritis, splenomegaly, hepatomegaly, leukocytosis, and acute-phase reaction) (P<0.01) in group II as compared with group III. We conclude that relapsing chronic enterocolitis and systemic complications are in part due to plasma K-K system activation, and that inhibition of this pathway is a potential therapeutic approach to human inflammatory bowel disease and associated extraintestinal manifestations.

Acute-Phase Proteins↗

PubMed2003

Human intestinal epithelial and smooth muscle cells are potent producers of IL-6.

BACKGROUND: Interleukin-6 (IL-6), a pluripotent cytokine, has traditionally been considered the product of proinflammatory cells. However, many other cell types have been shown to produce IL-6. Since intestinal inflammation is commonly associated with a vigorous systemic inflammatory response, we hypothesized that intestinal epithelial and smooth muscle cells might contribute to that response by producing IL-6. We therefore studied the capacity of differentiated human intestinal epithelial and smooth muscle cell lines to produce IL-6 in response to various proinflammatory stimuli. MATERIALS AND METHODS: CCL-241, a human intestinal epithelial cell line, and HISM, a human intestinal muscle cell line, were grown to confluency and then treated for 24 h with various concentrations of lipopolysaccharide, Clostridium difficile culture extract containing both toxin A and toxin B, recombinant human tumor necrosis factor-alpha (TNF-alpha), or recombinant human interleukin-1 beta (IL-1beta). Supernatants were then collected for IL-6 determination using an enzyme-linked immunosorbent assay. Cell numbers were determined using a Coulter counter. For comparison, parallel studies were performed using phorbol ester-primed U-937 and THP-1 human macrophage cell lines. RESULTS: Both human intestinal epithelial and smooth muscle cells produced IL-6 under basal conditions. In HISM cells, but not in CCL-241 cells, IL-6 release was increased slightly by treatment with C. difficile culture extract containing both toxin A and toxin B and with lipopolysaccharide. In both cell lines, IL-6 production was profoundly stimulated by treatment with IL-1beta and less so with TNF-alpha. Combinations of high-dose TNF-alpha and IL-1beta may have a slightly additive, but not synergistic, effect on IL-6 release. The amount of IL-6 produced by IL-1-stimulated intestinal cell lines was 70-fold higher than that produced by stimulated macrophage cell lines. CONCLUSIONS; Both intestinal epithelial and smooth muscle cells demonstrate the ability to release significant amounts of IL-6. The profound response to IL-1beta and TNF-alpha stimulation by both cell lines suggests that human intestinal parenchymal cells, influenced by paracrine mediators liberated from proinflammatory cells, might significantly contribute to the overall systemic inflammatory response by producing IL-6.

Bacterial Proteins↗

PubMed2000

Impaired mucosal defense to acute colonic injury in mice lacking cyclooxygenase-1 or cyclooxygenase-2.

To investigate roles in intestinal inflammation for the 2 cyclooxygenase (COX) isoforms, we determined susceptibility to spontaneous and induced acute colitis in mice lacking either the COX-1 or COX-2 isoform. We treated wild-type, COX-1(-/-), COX-2(-/-), and heterozygous mice with dextran sodium sulfate (DSS) to provoke acute colonic inflammation, and we quantified tissue damage, prostaglandin (PG) E(2), and interleukin-1beta. No spontaneous gastrointestinal inflammation was detected in mice homozygous for either mutation, despite almost undetectable basal intestinal PGE(2) production in COX-1(-/-) mice. Both COX-1(-/-) and COX-2(-/-) mice showed increased susceptibility to a low-dose of DSS that caused mild colonic epithelial injury in wild-type mice. COX-2(-/-) mice were more susceptible than COX-1(-/-) mice, and selective pharmacologic blockade of COX-2 potentiated injury in COX-1(-/-) mice. At a high dose, DSS treatment was fatal to 50% of the animals in each mutant group, but all wild-type mice survived. DSS treatment increased PGE(2) intestinal secretion in all groups except COX-2(-/-) mice. These results demonstrate that COX-1 and COX-2 share a crucial role in the defense of the intestinal mucosa (with inducible COX-2 being perhaps more active during inflammation) and that neither isoform is essential in maintaining mucosal homeostasis in the absence of injurious stimuli.

Animals↗

PubMed2002

[Intestines and joints: an entity?].

The intestinal inflammation and the inflammatory arthropathy in Crohn's disease and in spondyloarthropathy are tightly linked. Both forms of inflammation occur in clinical and subclinical forms in both diseases: 60% of patients with Crohn's disease have clinical and/or radiological signs of articular involvement--65% of patients belonging to the concept of spondyloarthropathy have endoscopic and/or histological signs of gut inflammation. The macrophages and the lymphocytes play a role either by the transport of bacterial antigens by macrophages from the gut to the synovium, either by the recirculation of activated lymphocytes attracted to the tissue by adhesion molecules. In both diseases, TNF alpha play a central role resulting in a rapid and spectacular improvement of the intestinal and articular inflammation by the administration of a monoclonal chimeric antibody directed against this cytokine (Infliximab). This clinical effect is associated or secondary to a restoration of the production of proinflammatory cytokines. According the importance of genetic factors in the etiopathogenesis of both diseases (mutation in the NOD2 gene for Crohn--HLA-B27 phenotype for spondyloarthropathy) future studies are necessary to find a common alteration explaining the link between gut and joint. This knowledge can help in the elucidation of the origin of both diseases.

Antibodies, Monoclonal↗

PubMed1999

Regulation of ICAM-1-mediated fibroblast-T cell reciprocal interaction: implications for modulation of gut inflammation.

BACKGROUND & AIMS: Immune-nonimmune cell interactions modulate mucosal immunity. We investigated the expression of adhesion molecules by intestinal fibroblasts, the effect of immune cell-derived factor on fibroblast binding of T cells, and the consequences of interfering with adhesion molecule expression on fibroblast-T cell interaction. METHODS: Expression of fibroblast intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 surface and messenger RNA (mRNA) was measured before and after exposure to immune cell-derived supernatants. Fibroblasts were treated with antibodies to ICAM-1 or VCAM-1, or ICAM-1 antisense oligonucleotide Isis 2302, before a T-cell adhesion assay. RESULTS: Fibroblast activation by immune cell-derived cytokines enhanced ICAM-1 and VCAM-1 surface expression and mRNA as well as adhesiveness for T cells. Blockade with neutralizing antibodies showed that binding was almost exclusively dependent on ICAM-1. Isis 2302 specifically reduced fibroblast ICAM-1 mRNA and dose-dependently inhibited ICAM-1 surface expression and T-cell binding. CONCLUSIONS: ICAM-1 is essential for intestinal fibroblast binding of T cells, a phenomenon that is efficiently and specifically disrupted by ICAM-1 antisense oligonucleotides. These observations emphasize the crucial regulatory role of fibroblasts in mucosal immunity and their potential as targets for therapeutic intervention in intestinal inflammation.

Blotting, Northern↗

PubMed1989

5-Aminosalicylic acid concentration in mucosal interstitium of cat small and large intestine.

Uncertainty regarding the concentration of 5-ASA within the mucosal interstitium has been a major limitation of defining the protective mechanisms of 5-ASA in intestinal inflammation. Therefore, we measured the concentration of 5-ASA in intestinal lymph and venous plasma during luminal perfusion of the cat small and large intestine with 10 mM 5-ASA. Blood and lymph flows were measured in each segment. 5-ASA and N-acetyl-5-ASA were extracted from plasma and lymph and quantified using fluorescence spectroscopy. Luminal perfusion of the terminal ileum with 5-ASA resulted in the following concentration profile: intestinal venous plasma (143 +/- 30 micrograms/ml) much greater than lymph (43 +/- 17 micrograms/ml) = systemic arterial plasma (40 +/- 11 micrograms/ml). In the colon the local venous plasma concentration of 5-ASA was 20 +/- 6 micrograms/ml compared to 2.0 +/- 1.0 micrograms/ml in systemic arterial plasma. N-Acetyl-5-ASA was found to comprise less than 5% of the total metabolite concentration in both ileum and colon. We also found that 58% of luminal 5-ASA was absorbed per minute in the terminal ileum, whereas only 3%/min was absorbed from the colon. The results of this study suggest that: (1) the mucosal interstitial concentration of 5-ASA in the terminal ileum and colon are approximately 100 micrograms/ml (654 microM) and 20 micrograms/ml (164 microM), respectively; and (2) the rate of 5-ASA absorption in the terminal ileum is approximately seven times greater than that in the colon.

Aminosalicylic Acids↗

PubMed1990

Transforming growth factor beta 1 selectively augments collagen synthesis by human intestinal smooth muscle cells.

Intestinal smooth muscle cells play a major role in the stricture formation that complicates chronic intestinal inflammation, by proliferating and producing collagen. Transforming growth factor beta 1 has been identified as an important inflammatory mediator in the fibrotic response of human tissue to inflammation. To determine whether this mediator might be involved in intestinal fibrosis, the effect of transforming growth factor beta 1 on collagen production and proliferation by human intestinal smooth muscle cells was studied in vitro. Cells in the second passage were grown to subconfluence in medium containing 10% Nu-Serum (Collaborative Research Inc., Bedford, MA), after which the concentration of Nu-Serum was decreased. Forty-eight hours later, transforming growth factor beta 1 was added to the culture medium to achieve concentrations of 1-500 pmol/L. After 24 hours exposure to the transforming growth factor beta 1, cellular collagen synthesis was determined by the uptake of [3H]proline into collagenase-sensitive protein. Transforming growth factor beta 1 caused a 100% increase in collagen production and a 40% increase in noncollagen protein production per cell, reflecting an increase in relative collagen synthesis of 58%. This effect was maximal at a concentration of 10 pmol/L. Epidermal growth factor, by comparison, had no significant effect on relative collagen synthesis. Transforming growth factor beta 1 caused a significant increase in the uptake of methylaminoisobutyric acid, a nonmetabolized amino acid analog, into the cells at 10 pmol/L. However, this effect was small (20% increase) compared with the effect on the uptake of proline into collagen (100% increase) at this concentration. When cell proliferation was examined by the uptake of [3H]thymidine, transforming growth factor beta 1 had no effect, whereas epidermal growth factor (1000 pmol/L) caused a 94% increase. Transforming growth factor beta 1 selectively augments collagen production by human intestinal smooth muscle cells in vitro. This effect is potent and is not related to effects on either cell proliferation or amino acid uptake. These data suggest that transforming growth factor beta 1 has an important role as an inflammatory mediator in the pathogenesis of intestinal fibrosis.

Cells, Cultured↗

PubMed2004

The lymphotoxin-beta receptor is critical for control of murine Citrobacter rodentium-induced colitis.

BACKGROUND AND AIMS: Lymphotoxin is a tumor necrosis factor-family cytokine. Blocking of lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor interactions prevents experimental colitis in mice, and this suggests a potential treatment principle of human inflammatory bowel disease. Infection of mice with Citrobacter rodentium serves as an animal model for human infectious colitis induced by enteropathogenic Escherichia coli . We studied the role of lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor signaling in Citrobacter rodentium -induced colitis. METHODS: Mice with disrupted lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor interactions secondary to gene defects (lymphotoxin-alpha -/- , lymphotoxin-beta -/- , and lymphotoxin-beta receptor -/- ) or treatment with the antagonist lymphotoxin-beta receptor-immunoglobulin G fusion protein were infected with Citrobacter rodentium . Body weight, fecal excretion of Citrobacter rodentium , and disease-related mortality were monitored. Spleen and liver organ cultures of mice assessed systemic infection. Intestinal inflammation and lymphoid architecture were histologically recorded in the large intestine, mesenteric lymph nodes, and spleen of infected mice. RESULTS: Inhibition of lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor interactions was associated with increased severity of Citrobacter rodentium -induced colitis, as indicated by increased disease-related mortality, more severe weight loss, intestinal bacterial abscesses, and a higher burden of Citrobacter rodentium in the spleen and liver of -/- and lymphotoxin-beta receptor-immunoglobulin G-treated mice. There was a reduction of CD11c + dendritic cells in the spleen of naive and infected -/- and lymphotoxin-beta receptor-immunoglobulin G-treated mice. In infected lymphotoxin-beta receptor -/- mice, anti- Citrobacter rodentium immunoglobulin G2a levels were decreased, whereas immunoglobulin G1 levels were increased. Citrobacter rodentium -induced interleukin-4 secretion was increased in lymphotoxin-beta receptor -/- mice. CONCLUSIONS: Lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor interactions are critical for immunity against Citrobacter rodentium in mice. Impaired anti-enteropathogenic Escherichia coli immunity may be anticipated in anti-lymphotoxin-beta receptor-directed therapy for human inflammatory bowel disease.

Animals↗

PubMed2004

Platelets in inflammatory bowel disease: clinical, pathogenic, and therapeutic implications.

Both Crohn's disease (CD) and ulcerative colitis (UC) are associated with abnormalities of platelet number and function. In the peripheral circulation the state of platelet activation is typically increased, and inflammatory bowel disease (IBD)-involved mucosa frequently contains platelet aggregates within mucosal microthrombi. The relevance of platelet dysfunction to IBD pathogenesis is still unclear, but there is solid evidence demonstrating that platelets, in addition to their traditional role in hemostasis, can also function as potent proinflammatory cells. Upon activation, platelets secrete a large number of biologically active molecules able to induce or amplify an inflammatory process through many of the same cellular and molecular pathways conventionally utilized by immune cells mediating IBD. The aim of this article is to review data on the existence of platelet dysfunction in IBD, substantiate platelets' inflammatory potential, discuss the implications of abnormal platelet activity for chronic intestinal inflammation, and consider the potential benefits of platelet modulation for treatment of IBD.

Blood Platelet Disorders↗

PubMed2003

Nuclear factor-kappa B activation promotes restitution of wounded intestinal epithelial monolayers.

Epithelial restitution, the movement of wound-edge cells into an area of epithelial cell denudation, is an important early step in the ulcer healing process. Growth factors regulate epithelial restitution, yet little is known about the transcriptional pathways that mediate their effects on cell migration. The transcription factor nuclear factor (NF)-kappaB is a master regulator of the host inflammatory response that is activated in the epithelium in intestinal inflammation, which often accompanies epithelial injury. We hypothesized that NF-kappaB may be an important transcriptional regulator of epithelial restitution. In an in vitro model of scrape-wounded monolayers of nontransformed rat intestinal epithelial (RIE-1) cells, NF-kappaB was activated in epithelial cells at the wound edge. Blocking of NF-kappaB activation by either pharmacological or genetic approaches inhibited intestinal epithelial restitution. Moreover, scrape wounding activated the epidermal growth factor receptor (EGFR) in cells at the wound edge, and, importantly, inhibiting EGFR tyrosine kinase activity decreased scrape wound-induced NF-kappaB activation and cell migration. These results indicate a novel role of NF-kappaB activation in a signaling pathway important for restitution and healing of intestinal epithelia. To the extent NF-kappaB may have parallel functions in vivo, they also suggest a need for caution in the proposed use of NF-kappaB inhibitors for the treatment of conditions associated with inflammation and injury of intestinal and other mucosal surfaces.

Animals↗

PubMed2002

Markers of inflammation in bacterial diarrhea among travelers, with a focus on enteroaggregative Escherichia coli pathogenicity.

The intestinal inflammatory response of traveler's diarrhea acquired in Goa, India, and Guadalajara, Mexico, was studied. Fecal lactoferrin was found in stool samples in which enteroaggregative Escherichia coli (EAEC), enterotoxigenic E. coli, or Salmonella or Shigella species were isolated, with Shigella-positive cases showing the highest level. Samples from cases of Shigella-associated diarrhea had the highest concentrations of fecal cytokines. Travelers to India who had EAEC-associated diarrhea showed elevated levels of interleukin (IL)-8 (median, 341.15 pg/mL) and IL-1beta (median, 749.90 pg/mL). Although 15 travelers to Mexico who had EAEC-associated diarrhea had a median concentration of 0 pg/mL for both IL-8 and IL-1beta, 2 had high levels of IL-8 (1853 and 11,786 pg/mL), and 5 showed elevated levels of IL-1beta (1-1240 pg/mL). Samples from patients in India who had pathogen-negative diarrhea or from patients in Mexico who had asymptomatic EAEC infection were negative for cytokines. Bacterial pathogens causing traveler's diarrhea commonly produce intestinal inflammation, although a subset of patients with EAEC-associated diarrhea fail to develop an inflammatory response.

Biomarkers↗

PubMed1997

Role of animal models for the pathogenesis and treatment of inflammatory bowel disease.

The etiology of chronic inflammatory bowel diseases (IBD) such as Crohn's disease and ulcerative colitis is still unknown. Recent studies including animal models of intestinal inflammation have identified interactions between the mucosal immune system, host genetic susceptibility and environmental factors, including normal intestinal microflora. Although the ideal animal model of IBD has not been found, each model can study pathogenetic factors such as acute intestinal injury and healing, acute and chronic inflammation, regulation by key cytokines, T-lymphocyte mediation, the role of luminal bacteria, immunoregulatory factors and genetic susceptibility. The relevance of these studies for the treatment of IBD is also discussed.

Animals↗

PubMed2026

Glial Connexin-43 Is a Pathogenic Mechanism Promoting Gut Inflammation in Postoperative Ileus Induced by Gut Surgical Manipulation With Potential Relevance to Humans.

BACKGROUND & AIMS: Abdominal surgery often precipitates postoperative ileus (POI), a frequent and severe gastrointestinal (GI) motility disorder, through mechanisms that involve intestinal inflammation. Emerging data show that enteric glia acquire a reactive phenotype that aggravates POI, but how glia exert this effect remains unclear. Enteric glia express connexin-43 hemichannels (gCx43), which are implicated in neurological and inflammatory disorders. Thus, we aimed to decipher contributions of glial connexin-43 (Cx43) in the pathophysiology of POI. METHODS: We induced POI in mice using in vivo intestinal manipulation and used glial Cx43cKO (Sox10CreERT2;Cx43fl/fl) or RiboTag (Sox10CreERT2/Rpl22HA/+) mice to evaluate Cx43-dependent signaling. Human enteric glial cultures (hEGC) and muscularis externa obtained during intestinal surgery translated findings to patients. Transcriptome analysis, immunofluorescence co-labeling, Western blots, and Cx43 hemichannel activation were used for quantitative analysis. RESULTS: Cx43 is the highest expressed connexin in enteric glia in mice and humans. Up-regulation of Cx43 occurs in various disease models linked to POI, GI surgical trauma, inflammation, immune cell activation, and enteric gliosis. In the mouse POI model, glial Cx43-deletion reduces glial reactivity, pro-inflammatory signals, upregulates host protection genes, regulates immune cell activation, and prevents enteric neuropathy. In hEGCs, interleukin (IL)-1β induction opens Cx43 and stimulates release of IL-6 and C-C motif ligand 2 (CCL2). The Cx43 peptide inhibitor, 43Gap26, inhibits glial Cx43 activation, reduces IL-6 release, and blocks upregulation of macrophage activation factors and immune cell regulation factors. Surgical intestinal trauma in patients upregulates Cx43 during inflammation and enteric gliosis in mouse POI. CONCLUSIONS: Glial Cx43 signaling promotes enteric gliosis, immune cell activation, inflammation, and enteric neuropathy in mice with potential translatability to humans after intestinal surgical trauma and mechanical stress in POI. Interventions that block glial Cx43 activation may be protective against POI development.

Animals↗