The inflammasomes play an important role in connecting the detection of endogenous and microbial danger signals to caspase-1 activation and induction of protective immune responses. NLRC4 is a cytosolic NOD-like receptor (NLR) that can trigger inflammasome formation in response to bacterial flagellin, an immunodominant antigen in the intestine. To characterize the role of NLRC4 in bacterially-triggered intestinal inflammation, we used the murine pathogen Citrobacter rodentium, an extracellular, attaching/effacing bacterium similar to EHEC and EPEC. Following infection with C. rodentium, we found that Nlrc4−/− mice developed more severe weight loss, increased bacterial colonization levels and exacerbated intestinal inflammation compared to WT counterparts. Nlrc4−/− mice mounted robust adaptive immune responses, but were unable to control early colonization by C. rodentium, suggesting that a defect in innate immunity was responsible. Experiments using bone marrow chimeras revealed that the protective effects of NLRC4 were dependent on its expression in non-hematopoietic cells and quantitative PCR analyses revealed that NLRC4 was highly expressed in epithelial crypts but not in intestinal stroma. Thus, early NLRC4 sensing in intestinal epithelial cells regulates colonization by an extracellular bacterial pathogen and limits subsequent intestinal damage.

Altered bacterial composition and small intestinal bacterial overgrowth (SiBo) may be associated with irritable bowel syndrome (IBS). This study aimed to determine the fecal and mucosa-associated bacterial composition along the gastrointestinal (GI) tract and to assess SIBO in IBS. Bacterial composition of feces, and mucosa of the duodenum and sigmoid colon was determined by 16S rRNAamplicon-sequencing. SIBO was evaluated by bacterial culture of duodenal aspirate, glucose and lactulose breath tests. Mucosal antibacterial gene expression was assessed by PCR Array. The bacterial profiles of feces and the mucosa of sigmoid colon, but not duodenum, differed between IBS patients (n = 17) and HS (n = 20). The IBS specific bacterial profiles were linked to the colonic antibacterial gene expression. Fecal bacterial profile differed between IBS subtypes, while the mucosa-associated bacterial profile was associated with IBS symptom severity and breath tests results at baseline (H 2 and/or cH 4 ≥ 15 ppm). The prevalence of SIBO was similar between IBS patients and HS. This study demonstrates that alterations in the bacterial composition of the sigmoid colon of iBS patients were linked to symptoms and immune activation. While breath tests reflected the mucosa-associated bacterial composition, there was no evidence for high prevalence of SIBO or small intestinal bacterial alterations in IBS.

1. Secreted mammalian Ly-6/urokinase plasminogen activator receptor-related protein-1 (SLURP-1) is a recently discovered endogenous ligand at the alpha7 subunit of the nicotinic acetylcholine receptors. Previous reports have shown that SLURP-1 is expressed in normal human keratinocytes seemingly with a pro-apoptotic function. Conversely, such expression was markedly attenuated in transformed cells and it was suggested that the molecule could convey protection against malignant transformation. 2. In this study, we demonstrated the mRNA expression (by RT-PCR) and protein expression (by Western blotting and immunocytochemistry) of SLURP-1 in the human colon cancer cell line, HT-29. 3. Furthermore, we demonstrated the expression of SLURP-1 (by immunohistochemistry) in tumour cells of human colon cancer tissue, and, to a greater extent, in immune and smooth muscle cells of adjacent, macroscopically tumour-free colon tissue. 4. The current findings suggest that SLURP-1 participates in the regulation of gut immune functions and motility, as well as possibly playing a role in colon carcinogenesis/cancer progression.

Background: Alteration of the host-microbiota cross talk at the intestinal barrier may participate in the pathophysiology of irritable bowel syndrome (IBS). Therefore, we aimed to determine effects of fecal luminal factors from IBS patients on the colonic epithelium using colonoids.Methods: Colon-derived organoid monolayers, colonoids, generated from a healthy subject, underwent stimulation with fecal supernatants from healthy subjects and IBS patients with predominant diarrhea, phosphate-buffered saline (PBS), or lipopolysaccharide (LPS). Cytokines in cell cultures and fecal LPS were measured by ELISA and mRNA gene expression of monolayers was analyzed using Qiagen RT 2 Profiler PCR Arrays. The fecal microbiota profile was determined by the GA-map ™ dysbiosis test and the fecal metabolite profile was analyzed by untargeted liquid chromatography/ mass spectrometry. Key results:Colonoid monolayers stimulated with fecal supernatants from healthy subjects (n = 7), PBS (n = 4) or LPS (n = 3) presented distinct gene expression profiles, with some overlap (R 2 Y = 0.70, Q 2 = 0.43). Addition of fecal supernatants from healthy subjects and IBS patients (n = 9) gave rise to different gene expression profiles of the colonoid monolayers (R 2 Y = 0.79, Q 2 = 0.64). Genes (n = 22) related to immune response (CD1D, TLR5) and barrier integrity (CLDN15, DSC2) contributed to the separation. Levels of proinflammatory cytokines in colonoid monolayer cultures were comparable when stimulated with fecal supernatants from either donor types.Fecal microbiota and metabolite profiles, but not LPS content, differed between the study groups.

The intestinal microbiota influences immune maturation during childhood, and is implicated in early-life allergy development. However, to directly study intestinal microbes and gut immune responses in infants is difficult. To investigate how different types of early-life gut microbiota affect immune development, we collected fecal samples from children with different allergic heredity (AH) and inoculated germ-free mice. Immune responses and microbiota composition were evaluated in the offspring of these mice. Microbial composition in the small intestine, the cecum and the colon were determined by 16S rRNA sequencing. The intestinal microbiota differed markedly between the groups of mice, but only exposure to microbiota associated with AH and known future allergy in children resulted in a T helper 17 (Th17)-signature, both systemically and in the gut mucosa in the mouse offspring. These Th17 responses could be signs of a particular microbiota and a shift in immune development, ultimately resulting in an increased risk of allergy.