Intestinal Epithelial Defense Research Articles

LncRNA Nostrill promotes interferon-γ-stimulated gene transcription and facilitates intestinal epithelial cell-intrinsic anti-Cryptosporidium defense.

Intestinal epithelial cells possess the requisite molecular machinery to initiate cell-intrinsic defensive responses against intracellular pathogens, including intracellular parasites. Interferons(IFNs) have been identified as cornerstones of epithelial cell-intrinsic defense against such pathogens in the gastrointestinal tract. Long non-coding RNAs (lncRNAs) are RNA transcripts (>200 nt) not translated into protein and represent a critical regulatory component of mucosal defense. We report here that lncRNA Nostrill facilitates IFN-γ-stimulated intestinal epithelial cell-intrinsic defense against infection by Cryptosporidium, an important opportunistic pathogen in AIDS patients and a common cause of diarrhea in young children. Nostrill promotes transcription of a panel of genes controlled by IFN-γ through facilitating Stat1 chromatin recruitment and thus, enhances expression of several genes associated with cell-intrinsic defense in intestinal epithelial cells in response to IFN-γ stimulation, including Igtp, iNos, and Gadd45g. Induction of Nostrill enhances IFN-γ-stimulated intestinal epithelial defense against Cryptosporidium infection, which is associated with an enhanced autophagy in intestinal epithelial cells. Our findings reveal that Nostrill enhances the transcription of a set of genes regulated by IFN-γ in intestinal epithelial cells. Moreover, induction of Nostrill facilitates the IFN-γ-mediated epithelial cell-intrinsic defense against cryptosporidial infections.

Defects in the expression of colonic host defense factors associate with barrier dysfunction induced by a high-fat/high-cholesterol diet.

The effect of Western diets in the gastrointestinal system is largely mediated by their ability to promote alterations in the immunity and physiology of the intestinal epithelium, and to affect the composition of the commensal microbiota. To investigate the response of the colonic epithelium to high-fat/high-cholesterol diets (HFHCDs), we evaluated the synthesis of host defense factors involved in the maintenance of the colonic homeostasis. C57BL/6 mice were fed an HFHCD for 3 weeks and their colons were evaluated for histopathology, gene expression, and microbiota composition. In addition, intestinal permeability and susceptibility to Citrobacter rodentium were also studied. HFHCD caused colonic hyperplasia, loss of goblet cells, thinning of the mucus layer, moderate changes in the composition of the intestinal microbiota, and an increase in intestinal permeability. Gene expression analyses revealed significant drops in the transcript levels of Muc1, Muc2, Agr2, Atoh1, Spdef, Ang4, Camp, Tff3, Dmbt1, Fcgbp, Saa3, and Retnlb. The goblet cell granules of HFHCD-fed mice were devoid of Relmβ and Tff3, indicating defective production of those two factors critical for intestinal epithelial defense and homeostasis. In correspondence with these defects, colonic bacteria were in close contact with, and invading the epithelium. Fecal shedding of C. rodentium showed an increased bacterial burden in HFHCD-fed animals accompanied by increased epithelial damage. Collectively, our results show that HFHCD perturbs the synthesis of colonic host defense factors, which associate with alterations in the commensal microbiota, the integrity of the intestinal barrier, and the host's susceptibility to enteric infections.

Gut symbionts dial up RA to prime host defense

In this issue of Cell Host & Microbe, Woo etal. (2021) show that retinoic acid generated by symbiotic segmented filamentous bacteria in the intestine primes host intestinal epithelial defense and mediates early innate immune protection against Citrobacter rodentium infection.

Cryptosporidial Infection Suppresses Intestinal Epithelial Cell MAPK Signaling Impairing Host Anti-Parasitic Defense.

Cryptosporidium is a genus of protozoan parasites that infect the gastrointestinal epithelium of a variety of vertebrate hosts. Intestinal epithelial cells are the first line of defense and play a critical role in orchestrating host immunity against Cryptosporidium infection. To counteract host defense response, Cryptosporidium has developed strategies of immune evasion to promote parasitic replication and survival within epithelial cells, but the underlying mechanisms are largely unclear. Using various models of intestinal cryptosporidiosis, we found that Cryptosporidium infection caused suppression of mitogen-activated protein kinase (MAPK) signaling in infected murine intestinal epithelial cells. Whereas expression levels of most genes encoding the key components of the MAPK signaling pathway were not changed in infected intestinal epithelial cells, we detected a significant downregulation of p38/Mapk, MAP kinase-activated protein kinase 2 (Mk2), and Mk3 genes in infected host cells. Suppression of MAPK signaling was associated with an impaired intestinal epithelial defense against C. parvum infection. Our data suggest that cryptosporidial infection may suppress intestinal epithelial cell MAPK signaling associated with the evasion of host antimicrobial defense.

A259 HIGH-FAT/HIGH-CHOLESTEROL DIETS PREDISPOSE THE HOST TO EXACERBATED ENTERIC INFECTIONS

Abstract Background High-fat/high-cholesterol diets are a well established risk factor for cardiovascular and metabolic diseases, given their propensity to trigger perturbations ranging from altering whole body lipid profile to the induction of intestinal dysbiosis. However much less is known about their effects on the host’s susceptibility to enteric infections. Aims To determine the effects of high-fat/high-cholesterol diets over the host’s susceptibility to enteric bacterial infections and identify the underlying molecular mechanisms. Methods C57BL/6 mice were given two different high-fat/high-cholesterol diets; HFHC (40% kcal fat, 1.25% cholesterol) or HFHCC (40% kcal fat, 1.25% cholesterol, 0.5% sodium cholate) and a control, normal diet (ND, 10% kcal fat, 0% cholesterol, 0% sodium cholate). After four weeks of administration, animals were euthanized and colonic tissue samples taken for histology, immunofluorescence, gene expression analyses, total protein lysates and microbiome sequencing (16S). A separated group of animals was gavaged with FITC-dextran to measure intestinal permeability. Mice fed with the diets for three weeks were infected with ~5x108 cfu of Citrobacter rodentium DBS100/StrpR by oral gavage, and kept on the corresponding diets after the infections. Bacterial shedding in the feces was followed for up to 30 days after infection. Results Administration of the HFHC and HFHCC diets caused an increase in intestinal permeability. Colonic sections stained with H&E and alcian blue evidenced a decreased in the number of mucin-filled goblet cells and a thinner mucus layer, suggesting a defect in the assembly and/or stability of the mucus layer. Expression analyses revealed a drop in the mRNA levels of Muc1 and Muc2, suggesting reduced mucin production. The concentration of IgA was slightly reduced in colon lysates and the transcript levels of the antimicrobial peptide genes Ang4, Leap2 and Cramp were also significantly reduced. Immunofluorescent microscopy showed that goblet cell granules of HFHC- and HFHCC-fed mice were devoid of Relmβ and Tff3, indicating defective production of those two factors critical for intestinal epithelial defense and homeostasis. Collectively, our results suggest that HFHC and HFHCC diets induce differentiation and functional defects in goblet cells. Fecal shedding of C. rodentium showed an increased bacterial burden in HFHC- and HFHCC-fed animals, indicating a more aggressive bacterial infection, accompanied by increased epithelial damage. Conclusions Consumption of high-fat/high cholesterol diets perturb the colonic homeostasis and alter intestinal defenses and the integrity of the intestinal barrier, predisposing the host to a higher susceptibility to enteric infections. Funding Agencies CIHRNSERC

Impaired antimicrobial response and mucosal protection induced by ibuprofen in the immature human intestine.

The use of nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin (INDO) and ibuprofen (IBU) has been shown to be an effective therapy for the closure of patent ductus arteriosus (PDA). However, this treatment has been associated with an increased risk of developing enteropathies in neonates. Whether the use of IBU is safer than INDO for the immature intestine remains to be elucidated. The direct impact of IBU on the human immature intestinal transcriptome was investigated using serum-free organ culture. Differentially expressed genes were analyzed with Ingenuity Pathway Analysis software and compared with those previously reported with INDO. Validation of differentially expressed genes was confirmed by qPCR. We identified several biological processes that were significantly modulated by IBU at similar levels to what had previously been observed with INDO, while the expression of genes involved in "antimicrobial response" and "mucus production" was significantly decreased exclusively by IBU in the immature intestine. Our findings indicate that IBU has a harmful influence on the immature intestine. In addition to exerting many of the INDO observed deleterious effects, IBU alters pathways regulating microbial colonization and intestinal epithelial defense.

Modulation of Intestinal Epithelial Defense Responses by Probiotic Bacteria

Probiotics are live microorganisms, which when administered in food confer numerous health benefits. In previous studies about beneficial effects of probiotic bacteria to health, particularly in the fields of intestinal mucosa defense responses, specific probiotics, in a strain-dependent manner, show certain degree of potential to reinforce the integrity of intestinal epithelium and/or regulate some immune components. The mechanism of probiotic action is an area of interest. Among all possible routes of modulation by probiotics of intestinal epithelial cell-mediated defense responses, modulations of intestinal barrier function, innate, and adaptive mucosal immune responses, as well as signaling pathways are considered to play important role in the intestinal defense responses against pathogenic bacteria. This review summarizes the beneficial effects of probiotic bacteria to intestinal health together with the mechanisms affected by probiotic bacteria: barrier function, innate, and adaptive defense responses such as secretion of mucins, defensins, trefoil factors, immunoglobulin A (IgA), Toll-like receptors (TLRs), cytokines, gut associated lymphoid tissues, and signaling pathways.

Recent Insights Into the Genetics of Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) are complex, multifactorial disorders that comprise Crohn's disease (CD) and ulcerative colitis (UC). Genome-wide association studies have identified approximately 100 loci that are significantly associated with IBD. These loci implicate a diverse array of genes and pathophysiologic mechanisms, including microbe recognition, lymphocyte activation, cytokine signaling, and intestinal epithelial defense. Consistent with epidemiologic predictions, many IBD-associated loci demonstrate genome-wide significant associations to both CD and UC, notably, genes whose products function in the interleukin-23 pathway, and transcription factors, including NK2 transcription factor related, locus 3 (NKX2-3), SMAD3, STAT3, ZMIZ1, and c-REL. Although CD and UC are both associated with genomic regions that implicate products of genes involved in leukocyte trafficking, there is evidence for association patterns that are distinct between CD and UC. CD-predominant associations include NOD2 and genes that regulate autophagy. In UC, the predominant association signal is on chromosome 6p21, in the major histocompatibility complex region, near HLA class II genes. UC-predominant loci have also implicated genes mediating epithelial defense function. There is a striking overlap of loci between diseases, which could provide comparative insight into mechanisms of disease pathogenesis. Genes that encode factors that function in the interleukin-23 pathway have been associated with a number of chronic inflammatory diseases, notably psoriasis and ankylosing spondylitis. Distinct genetic associations indicate that the colitis associated with primary sclerosing cholangitis is pathophysiologically distinct from UC that is not associated with primary sclerosing cholangitis. As many as 14 susceptibility loci are shared between IBD and celiac disease, indicating significant overlap in pathophysiology. Future genetic studies will be directed toward identifying uncommon variations with potentially greater statistical effects, defining population differences, and more completely accounting for familial transmission of disease.

A Key Role for E-cadherin in Intestinal Homeostasis and Paneth Cell Maturation

BackgroundE-cadherin is a major component of adherens junctions. Impaired expression of E-cadherin in the small intestine and colon has been linked to a disturbed intestinal homeostasis and barrier function. Down-regulation of E-cadherin is associated with the pathogenesis of infections with enteropathogenic bacteria and Crohn's disease.Methods and FindingsTo genetically clarify the function of E-cadherin in intestinal homeostasis and maintenance of the epithelial defense line, the Cdh1 gene was conditionally inactivated in the mouse intestinal epithelium. Inactivation of the Cdh1 gene in the small intestine and colon resulted in bloody diarrhea associated with enhanced apoptosis and cell shedding, causing life-threatening disease within 6 days. Loss of E-cadherin led cells migrate faster along the crypt-villus axis and perturbed cellular differentiation. Maturation and positioning of goblet cells and Paneth cells, the main cell lineage of the intestinal innate immune system, was severely disturbed. The expression of anti-bacterial cryptidins was reduced and mice showed a deficiency in clearing enteropathogenic bacteria from the intestinal lumen.ConclusionThese results highlight the central function of E-cadherin in the maintenance of two components of the intestinal epithelial defense: E-cadherin is required for the proper function of the intestinal epithelial lining by providing mechanical integrity and is a prerequisite for the proper maturation of Paneth and goblet cells.

Intestinal epithelial defense systems protect against bacterial threats.

Numerous bacterial species inhabit the lumen of the human intestine. The epithelial cells that line the intestinal barrier are in direct contact with many of these species and have developed sophisticated strategies to prevent bacterial invasion of host tissue beyond simply providing a physical blockade. Intestinal epithelial cells (IECs) possess receptors that are capable of recognizing bacterial products, and engagement of these receptors results in the production and secretion of immunoregulatory proteins, such as cytokines and chemokines, which mobilize immune effector cells, including macrophages, dendritic cells, and neutrophils. In addition, IECs can produce various lipid-based eicosanoids that can contribute to the orchestration of the immune response. A better understanding of how the intestinal epithelium interacts with its microbial constituents may provide insight into strategies for treatment of enteric infections and inflammatory bowel disease.