Inflammatory bowel disease (IBD) is a progressive disease that includes Crohn's diseases and ulcerative colitis. Over one third of IBD patients have secondary organ pathologies and pulmonary manifestations are common. The platelet activating factor receptor (PAFR) plays a critical role in regulating inflammation and it is expressed on epithelial cells and neutrophils in both colon and lung. Having identified increased expression of PAFR in both the gastrointestinal (GI) tract and lungs of mice with dextran sulfate sodium (DSS) colitis, we hypothesised that PAFR was a mediator of the pulmonary inflammation associated with colitis. We aimed to elucidate the role of PAFR in gut‐lung inflammatory cross‐talk using of the DSS‐induced experimental model of colitis (7 days). DSS mice were treated with PAFR antagonist CV6209 both intranasally and intravenously and lung, colon and blood were assessed for inflammatory cells and mediators by qPCR, immunoblot, immunohistochemistry and flow cytometry. We demonstrated that DSS‐induced colitis resulted in inflammation in mouse bronchoalveolar lavage fluid (BALF) and lungs, as well as increased PAFR protein levels in lungs and colons. Pulmonary neutrophils in DSS animals showed increased PAFR staining. Bacterial 16S mRNA expression were also increased in mouse lungs after 7 days DSS challenge. Both intravenous and intranasal inhibition of PAFR by CV6209 reduced colitis‐induced numbers of neutrophils, but not macrophages, in mouse lungs. Inhibition of PAFR also reduced levels of TNF and IL‐1b proteins and bacterial 16S expression in mouse lungs. Importantly, intravenous administration of CV6209 reduced colitis pathology, TNF and IL‐1b protein levels in mouse colons after 7 days DSS challenge. In the DSS model, increased PAFR protein expression was associated with inflammasome activation, characterized by increased NLRP3 and mature caspase‐1 proteins, however inhibition of PAFR by CV6209 reduced NLRP3 and caspase‐1 levels after DSS challenge in mouse lungs. In vitro, NLRP3, activated caspase‐1 and secreted IL‐1b protein levels were increased in human alveolar epithelial cell culture (A549) after 24h LPS stimulation, and this was inhibited by treatment with CV6209. These data suggest that PAFR regulates colitis‐induced lung inflammation by IL‐1b protein activation via the NLRP3 inflammasome signalling pathway. PAFR may act as an inflammasome‐activating pattern recognition receptor during mucosal inflammation thus is a potential therapeutic target for lung inflammation associated with colitis and bacteraemia. Support or Funding Information This study was supported by a grant from National Health Medical Research Council (NHMRC) Australia This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Inflammatory bowel disease (IBD) is associated with several immune-mediated extraintestinal manifestations. More than half of all IBD patients have some form of respiratory pathology, most commonly neutrophil-mediated diseases, such as bronchiectasis and chronic bronchitis. Using murine models of colitis, we aimed to identify the immune mechanisms driving pulmonary manifestations of IBD. We found increased neutrophil numbers in lung tissue associated with the pulmonary vasculature in both trinitrobenzenesulfonic acid- and dextran sulfate sodium-induced models of colitis. Analysis of systemic inflammation identified that neutrophilia was associated with bacteremia and pyrexia in animal models of colitis. We further identified IL-6 as a systemic mediator of neutrophil recruitment from the bone marrow of dextran sulfate sodium animals. Functional inhibition of IL-6 led to reduced systemic and pulmonary neutrophilia, but it did not attenuate established colitis pathology. These data suggest that systemic bacteremia and pyrexia drive IL-6 secretion, which is a critical driver for pulmonary manifestation of IBD. Targeting IL-6 may reduce neutrophil-associated extraintestinal manifestations in IBD patients.

Inflammasomes are cytosolic, multimeric protein complexes capable of activating pro‐inflammatory cytokines such as IL‐1β and IL‐18, which play a key role in host defence. Inflammasome components are highly expressed in the intestinal epithelium. In recent years, studies have begun to demonstrate that epithelial‐intrinsic inflammasomes play a critical role in regulating epithelial homeostasis, both by defending the epithelium from pathogenic insult and through the regulation of the mucosal environment. However, the majority of research regarding inflammasome activation has focused on professional immune cells, such as macrophages. Here, we present an overview of the current understanding of inflammasome function in epithelial cells and at mucosal surfaces and, in particular, in the intestine.

Intestinal epithelia are critical for maintaining gastrointestinal homeostasis. Epithelial barrier injury, causing inflammation and vascular damage, results in inflammatory hypoxia and thus healing occurs in an oxygen-restricted environment. The transcription factor hypoxia inducible factor (HIF)-1 regulates genes important for cell survival and repair, including the cell adhesion protein β1-integrin. Integrins function as αβ-dimers and α-integrin-matrix binding is critical for cell migration. We hypothesized that HIF-1 stabilization accelerates epithelial migration through integrin-dependent pathways. We aimed to examine functional and post-translational activity of α-integrins during HIF-1-mediated intestinal epithelial healing. Wound healing was assessed in T84 monolayers over 24 hours with/without prolyl-hydroxylase inhibitor (PHDi) (GB-004), which stabilizes HIF-1. Gene and protein expression were measured by RT-PCR and immunoblot, α-integrin localization was assessed by immunofluorescence. α-integrin function was assessed by antibody-mediated blockade and integrin-α6 regulation was determined by HIF-1α chromatin immunoprecipitation. Models of mucosal wounding and TNBS-induced colitis were used to examine integrin expression and localization in vivo. PHDi-treatment accelerated wound closure and migration within 12 hours, associated with increased integrin-α2 and α6 protein, but not α3. Functional blockade of integrins-α2 and α6 inhibited PHDi-mediated accelerated wound closure. HIF-1 bound directly to the integrin-α6 promoter. PHDi treatment accelerated mucosal healing, which was associated with increased α6 immunohistochemical staining in wound-associated epithelium and wound-adjacent tissue. PHDi-treatment increased α6 protein levels in colonocytes of TNBS mice and induced α6 staining in regenerating crypts and re-epithelialized inflammatory lesions. Together these data demonstrate a role for HIF-1 in regulating both integrin-α2 and α6 responses during intestinal epithelial healing.

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BackgroundFunctional dyspepsia is characterised by chronic symptoms of post-prandial distress or epigastric pain not associated with defined structural pathology. Increased peripheral gut-homing T cells have been previously identified in patients. To date, it is unknown if these T cells were antigen-experienced, or if a specific phenotype was associated with FD.ObjectiveThis study aimed to characterise T cell populations in the blood and duodenal mucosa of FD patients that may be implicated in disease pathophysiology.MethodsWe identified duodenal T cell populations from 23 controls and 49 Rome III FD patients by flow cytometry using a surface marker antibody panel. We also analysed T cell populations in peripheral blood from 37 controls and 61 patients. Where available, we examined the number of duodenal eosinophils in patients and controls.ResultsThere was a shift in the duodenal T helper cell balance in FD patients compared to controls. For example, patients had increased duodenal mucosal Th2 populations in the effector (13.03 ± 16.11, 19.84 ± 15.51, p=0.038), central memory (23.75 ± 18.97, 37.52 ± 17.51, p=0.007) and effector memory (9.80±10.50 vs 20.53±14.15, p=0.001) populations. Th17 populations were also increased in the effector (31.74±24.73 vs 45.57±23.75, p=0.03) and effector memory (11.95±8.42 vs 18.44±15.63, p=0.027) subsets. Peripheral T cell populations were unchanged between FD and control.ConclusionOur findings identify an association between lymphocyte populations and FD, specifically a Th2 and Th17 signature in the duodenal mucosa. The presence of effector and memory cells suggest that the microinflammation in FD is antigen driven.

In this study, the intestinal permeability of metal(loid)s (MLs) such as arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg) was examined, as influenced by gut microbes and chelating agents using an in vitro gastrointestinal/Caco-2 cell intestinal epithelium model. The results showed that in the presence of gut microbes or chelating agents, there was a significant decrease in the permeability of MLs (As-7.5%, Cd-6.3%, Pb-7.9% and Hg-8.2%) as measured by apparent permeability coefficient value (Papp), with differences in ML retention and complexation amongst the chelants and the gut microbes. The decrease in ML permeability varied amongst the MLs. Chelating agents reduce intestinal absorption of MLs by forming complexes thereby making them less permeable. In the case of gut bacteria, the decrease in the intestinal permeability of MLs may be associated to a direct protection of the intestinal barrier against the MLs or indirect intestinal ML sequestration by the gut bacteria through adsorption on bacterial surface. Thus, both gut microbes and chelating agents can be used to decrease the intestinal permeability of MLs, thereby mitigating their toxicity.

Objectives: Gastrointestinal (GI) inflammation and GI integrity deficits are common comorbidities of neuropsychiatric disorders. Ongoing research suggests that these aberrations may be contributing to heightened immune signals that have the potential to disrupt neuronal homeostasis and exacerbate behavioural deficits. The current study aimed to determine whether the well-characterized animal model of neuropsychopathology, the maternal immune activation (MIA) model, produced GI inflammation and integrity disruptions in association with anxiety-like behaviour. Methods: Pregnant Wistar rats were exposed to the viral mimetic polyriboinosinic:polyribocytidilic acid (polyI:C) on gestational days (GD) 10 and 19. Evidence of ANS activation, GI inflammation, and GI barrier integrity was assessed in both neonatal (postnatal day, P7) and adult (P84) offspring. Anxiety-like behaviour was assessed at P100. Results: Neonatal MIA offspring exhibited an altered intestinal inflammatory profile and evidence of an increase in lymphoid aggregates. MIA neonates also displayed disruptions to GI barrier tight junction protein mRNA. In addition, adult MIA offspring exhibited an increase in anxiety-like behaviours. Conclusion: These results indicate that the MIA rat model, which is well documented to produce behavioural, neurochemical, and neuroanatomical abnormalities, also produces GI inflammation and integrity disruptions. We suggest that this model may be a useful tool to elucidate biological pathways associated with neuropsychiatric disorders.