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Increased T helper (Th)1/Th17 immune responses are a hallmark of Crohn’s disease (CD) immunopathogenesis. CD90+ (myo-)fibroblasts (MFs) are abundant cells in the normal (N) intestinal mucosa contributing to mucosal tolerance via suppression of Th1 cell activity through cell surface membrane-bound PD-L1 (mPD-L1). CD-MFs have a decreased level of mPD-L1. Consequently, mPD-L1-mediated suppression of Th1 cells by CD-MFs is decreased, yet the mechanism responsible for the reduction in mPDL-1 is unknown. Increased expression of matrix metalloproteinases (MMPs) has been reported in CD. Herein we observed that when compared to N- and ulcerative colitis (UC)-MFs, CD-MFs increase in LPS-inducible levels of MMP-7 and -9 with a significant increase in both basal and inducible MMP-10. A similar pattern of MMP expression was observed in the CD-inflamed mucosa. Treatment of N-MFs with a combination of recombinant human MMP-7, -9 and -10 significantly decreased mPD-L1. In contrast, inhibition of MMP activity with MMP inhibitors or anti-MMP-10 neutralizing antibodies restores mPD-L1 on CD-MFs. CD-MFs demonstrated reduced capacity to suppress Th1 and Th17 responses from activated CD4+ T cells. By contrast, supplementation of the CD-MF:T-cell co-cultures with MMP inhibitors or anti-MMP neutralizing antibodies restored the CD-MF-mediated suppression. Our data suggest that (i) increased MMP-10 expression by CD-MFs and concomitant cleavage of PD-L1 from the surface of CD-MFs are likely to be one of the factors contributing to the decrease of mPD-L1-mediated suppression of Th1/Th17 cells in CD; and (ii) MMPs are likely to have a significant role in the intestinal mucosal immune responses.

The role of programmed cell death protein 1 (PD-1) and its ligands in the dysregulation of T helper immune responses observed in the inflammatory bowel disease (IBD) is unclear. Recently, a novel concept emerged that CD90Tissues and cells derived from Crohn's disease (CD), ulcerative colitis (UC), and healthy individuals (N) were studiedA significant increase in programmed death-ligand 1 (PD-L1) was observed in the inflamed UC colonic mucosa when compared to the non-inflamed matched tissue samples, CD, and healthy controls. UC-CMFs were among the major populations in the colonic mucosa contributing to the enhanced PD-L1 expression. In contrast, PD-L1 expression was decreased in CD-CMFs. When compared to CD-CMFs and N-CMFs, UC-CMFs demonstrated stronger suppression of IL-2, Th1 transcriptional factor Tbet, and IFN-γ expression by CD3/CD28-activated CD4We present evidence showing that increased PD-L1 expression suppresses Th1 cell activity in UC. In contrast, loss of PD-L1 expression observed in CD contributes to the persistence of the Th1 inflammatory milieu in CD. Our data suggest that dysregulation of the Th1 responses in the inflamed colonic mucosa of IBD patients is promoted by the alterations in PD-L1 expression in the mucosal mesenchymal stromal cell compartment.

Background Abdominal pain is one of the major symptoms of inflammatory Bowel Disease (IBD). The inflammatory mediators released by colon inflammation are known to sensitize the afferent neurons, which is one of the contributors to abdominal pain. However, not all IBD patients have abdominal pain, and some patients report abdominal pain during remission, suggesting contributions of other pathological factors to abdominal pain in IBD. Epidemiological studies found early-life gastrointestinal infections a risk factor for IBD symptoms and adult-life gastrointestinal infections may trigger the onset of IBD. We investigated the hypothesis that neonatal colon immune challenge followed by an adult colon immune challenge upregulates spinal cord BDNF that aggravates visceral sensitivity over and above that induced by adult colon immune challenge alone. Methods We induced neonatal and adult colon immune challenges by intraluminal administration of trinitrobenzene sulfonic acid to the rat colon. Key Results We found that neonatal immune challenge triggers epigenetic programming that upregulates tyrosine hydroxylase in the locus ceruleus when these rats are subjected to an adult colon immune challenge. The upregulation of locus ceruleus tyrosine hydroxylase, upregulates norepinephrine in the cerebrospinal fluid that acts on adrenergic receptors to enhance pCREB binding to the cAMP response element, which recruits histone acetylene transferase (HAT) to the BDNF gene to enhance its transcription resulting in aggravated visceromotor response to colorectal distension. HAT and adrenergic receptor antagonists block the aggravation of visceral sensitivity. Conclusion & Inferences HAT and adrenergic receptor inhibitors may serve as alternates to opioids and NSAIDS in suppressing abdominal pain in IBD.

Nucleotide oligomerization domain 2 (NOD2) functions as a mammalian cytosolic pathogen recognition molecule, and variants have been associated with risk for Crohn disease. We recently demonstrated that NOD2 functions as an anti-bacterial factor limiting survival of intracellular invasive bacteria. To gain further insight into the mechanism of NOD2 activation and signal transduction, we performed yeast two-hybrid screening. We demonstrate that GRIM-19, a protein with homology to the NADPH dehydrogenase complex, interacts with endogenous NOD2 in HT29 cells. GRIM-19 is required for NF-kappaB activation following NOD2-mediated recognition of bacterial muramyl dipeptide. GRIM-19 also controls pathogen invasion of intestinal epithelial cells. GRIM-19 expression is decreased in inflamed mucosa of patients with inflammatory bowel diseases. GRIM-19 may be a key component in NOD2-mediated innate mucosal responses and serve to regulate intestinal epithelial cell responses to microbes.

Nucleotide oligomerization domain (NOD) 2 functions as a mammalian cytosolic pathogen recognition molecule, and mutant forms have been genetically linked to Crohn's disease (CD). NOD2 associates with the caspase activation and recruitment domain of RIP-like interacting caspase-like apoptosis regulatory protein kinase (RICK)/RIP2 and activates nuclear factor (NF)–κB in epithelial cells and macrophages, whereas NOD2 mutant 3020insC, which is associated with CD, shows an impaired ability to activate NF-κB. To gain insight into the molecular mechanisms of NOD2 function, we performed a functional analysis of deletion and substitution NOD2 mutants. NOD2, but not NOD2 3020insC mutant, associated with cell surface membranes of intestinal epithelial cells. Membrane targeting and subsequent NF-κB activation are mediated by two leucine residues and a tryptophan-containing motif in the COOH-terminal domain of NOD2. The membrane targeting of NOD2 is required for NF-κB activation after the recognition of bacterial muramyl dipeptide in intestinal epithelial cells.

The etiologies of functional dyspepsia symptoms, including postprandial distress syndrome, remain unknown. We tested the hypothesis that neonatal colon inflammation induces postprandial distress syndrome-like symptoms in adult life that associate with increased activation of vagal afferent pathways and forebrain limbic regions.These rats showed a significant decrease in nutrient meal consumption to satiety after an overnight fast, decrease in gastric emptying, decrease in total distance traveled, and decrease in percent distance traveled in midfield versus control rats in open field test, indicating postprandial anxiety- and depression-like behaviors. Adult naïve rats treated with oral iodoacetamide to induce H. pylori-like mild gastritis demonstrated similar postprandial effects as the above rats.We concluded that neonatal colon inflammation is a risk factor for the development of postprandial distress syndrome-like symptoms. While mild gastritis can induce symptoms similar to those of neonatal colon inflammation, gastritis in these rats does not worsen the symptoms.