Unknown,Transcriptomics,Genomics,Proteomics

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The Tight Junction Protein Claudin-2 Controls Mucosal Permeability, Immune Tolerance and Colitis in Mice

ABSTRACT: The mucosal epithelium plays a key role in regulating immune homeostasis. Dysregulation of epithelial barrier function is associated with mucosal inflammation. Expression of claudin-2, a pore-forming tight junction protein, is highly upregulated during inflammatory bowel disease (IBD) and, due to its association with epithelial permeability, has been postulated to promote inflammation. Furthermore, claudin-2 also regulates colonic epithelial cell proliferation and intestinal nutrient absorption. However, the precise role of claudin-2 in regulating colonic epithelial and immune homeostasis remains unclear. Here, we demonstrate, using Villin-Claudin-2 transgenic (Cl-2TG) mice, that increased colonic claudin-2 expression unexpectedly protects mice against experimentally induced colitis and colitis-associated cancer. Notably, Cl-2TG mice exhibited increased colon length and permeability as compared with wild type (WT) littermates. However, despite their leaky colon, Cl-2TG mice subjected to experimental colitis were immune compromised, with reduced induction of TLR-2, TLR-4, Myd-88 expression and NF-kB and STAT3 activation. Most importantly, colonic macrophages in Cl-2TG mice exhibited an anergic phenotype. Claudin-2 overexpression also increased colonocyte proliferation and provided protection against colitis-induced colonocyte death. Taken together, our findings have revealed a critical role of claudin-2 in regulating colonic homeostasis, suggesting novel therapeutic strategies for inflammatory conditions of the gastrointestinal tract. 8-10 weeks old male Villin-Claudin-2 transgenic mice and WT littermates were provided either normal drinking water (control) or Dextran Sodium Sulfate (DSS: 4% w/v) for 10 days. 3 replicates each.

ORGANISM(S): Mus musculus

SUBMITTER: amar singh

PROVIDER: E-GEOD-46006 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Histone deacetylases (Hdac) remove acetyl groups from proteins, influencing global and specific gene expression. Hdacs control inflammation, as shown by Hdac inhibitor-dependent protection from DSS-induced murine colitis. While tissue-specific Hdac knockouts show redundant and specific functions, little is known of their intestinal epithelial cell (IEC) role. We have shown previously that dual Hdac1/Hdac2 IEC-specific loss disrupts cell proliferation and determination, with decreased secretory cell numbers and altered barrier function. We thus investigated how compound Hdac1/Hdac2 or Hdac2 IEC-specific deficiency alters the inflammatory response. Floxed Hdac1 and Hdac2 and villin-Cre mice were interbred. Compound Hdac1/Hdac2 IEC-deficient mice showed chronic basal inflammation, with increased basal Disease Activity Index (DAI) and deregulated Reg gene colonic expression. DSS-treated dual Hdac1/Hdac2 IEC-deficient mice displayed increased DAI, histological score, intestinal permeability and inflammatory gene expression. In contrast to double knockouts, Hdac2 IEC-specific loss did not affect IEC determination and growth, nor result in chronic inflammation. However, Hdac2 disruption protected against DSS colitis, as shown by decreased DAI, intestinal permeability and caspase-3 cleavage. Hdac2 IEC-specific deficient mice displayed increased expression of IEC gene subsets, such as colonic antimicrobial Reg3b and Reg3g mRNAs, and decreased expression of immune cell function-related genes. Our data show that Hdac1 and Hdac2 are essential IEC homeostasis regulators. IEC-specific Hdac1 and Hdac2 may act as epigenetic sensors and transmitters of environmental cues and regulate IEC-mediated mucosal homeostatic and inflammatory responses. Different levels of IEC Hdac activity may lead to positive or negative outcomes on intestinal homeostasis during inflammation Total RNAs from the colon of three control and three Hdac2 IEC-specific knockout mice were isolated with the Rneasy kit (Qiagen, Mississauga, ON, Canada).

Project description:Background & Aims: HNF4Î± is an important transcriptional regulator of hepatocyte and pancreatic function. Hnf4Î± deletion is embryonically lethal with severe defects in visceral endoderm formation, liver maturation and colon development. However, the precise role of this transcription factor in maintaining homeostasis of the adult intestine remains unclear. Herein, we aimed to elucidate the adult intestinal functions of Hnf4Î±. Methods: A conditional intestinal epithelial Hnf4Î± knockout mouse was generated. Histological abnormality of the colonic mucosa was assessed by immunodetection and Western. Changes in global gene expression and biological network were analyzed. Results: Hnf4Î± intestine null mice developed normally until reaching young adulthood. Crypt distortion became apparent in the Hnf4Î± null colon at 3 months of age followed by focal areas of crypt dropout, increased immune cell infiltrates, crypt hyperplasia and early signs of polyposis later in life. A gene profiling analysis identified cell death and cell cycle related to cancer as the most significant sets of genes altered in the Hnf4Î± colon null mice. Expression levels of the tight junction proteins claudin 4, 8 and 15 were altered early in the colon epithelium of Hnf4Î± mutants and correlated with increased barrier permeability to a molecular tracer that does not normally penetrate normal mucosa. Conclusion: These observations support a functional role for Hnf4Î± in protecting the colonic mucosa against the initiation of the changes resembling inflammatory bowel diseases and polyp formation. Experiment Overall Design: HNF4alpha was conditionally knockout in the mouse epithelial colon with the villin CRE. A total of 3 control and 3 mutant littermates individuals were sacrificed at 1 year of age. The colon was harvested and Total RNA was isolated from each individuals. Each RNA sample was independently used to generate probes to screen affymetrix chips.

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The Tight Junction Protein Claudin-2 Controls Mucosal Permeability, Immune Tolerance and Colitis in Mice

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