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

E-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. To 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. These 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

C57Bl/6 N mice on a western diet display reduced intestinal and hepatic cholesterol levels despite a plasma hypercholesterolemia

Abstract Background Small intestine and liver greatly contribute to whole body lipid, cholesterol and phospholipid metabolism but to which extent cholesterol and phospholipid handling in these tissues is affected by high fat Western-style obesogenic diets remains to be determined. Methods We therefore measured cholesterol and phospholipid concentration in intestine and liver and quantified fecal neutral sterol and bile acid excretion in C57Bl/6 N mice fed for 12 weeks either a cholesterol-free high carbohydrate control diet or a high fat Western diet containing 0.03% (w/w) cholesterol. To identify the underlying mechanisms of dietary adaptations in intestine and liver, changes in gene expression were assessed by microarray and qPCR profiling, respectively. Results Mice on Western diet showed increased plasma cholesterol levels, associated with the higher dietary cholesterol supply, yet, significantly reduced cholesterol levels were found in intestine and liver. Transcript profiling revealed evidence that expression of numerous genes involved in cholesterol synthesis and uptake via LDL, but also in phospholipid metabolism, underwent compensatory regulations in both tissues. Alterations in glycerophospholipid metabolism were confirmed at the metabolite level by phospolipid profiling via mass spectrometry. Conclusions Our findings suggest that intestine and liver react to a high dietary fat intake by an activation of de novo cholesterol synthesis and other cholesterol-saving mechanisms, as well as with major changes in phospholipid metabolism, to accommodate to the fat load.</p

Loss of differentiated cells following loss of E-cadherin.

<p>(A and B) Staining of absorptive enterocytes for villin. Reduced staining intensity and disruption of the epithelial lining (arrowheads) in the small intestine (A) and colon (B) of Cre⁺<i>Cdh1</i>^fl/fl (KO) mice as compared to controls (WT). (C and D) PAS staining revealed a strong reduction of goblet cells (arrowheads) in the colon (C) and small intestine (D) of Cre⁺<i>Cdh1</i>^fl/fl mice four days after start of induction of recombination as compared to control mice. (E and F) Paneth cells were identified by immunostaining for lysozyme (E) and MMP7 (F). After five days of tamoxifen treatment, Paneth cells remained confined to the base of the crypt in control mice, but were distributed throughout the crypt-villus axis in Cre⁺<i>Cdh1</i>^fl/fl mice (arrowheads). Bars in A–F, 100 µm.</p

E-cadherin is required for the maintenance of the intestinal epithelial architecture.

<p>(A) Deletion of E-cadherin results in severe loss of body weight in Cre⁺<i>Cdh1</i>^fl/fl mice (n = 4) as compared to gender-matched littermates (n = 6) (<i>P</i><0.005). Necropsy revealed a reduction of (B) wet weight (<i>P</i> = 0.066) and (C) the length of small intestine (<i>P</i> = 0.027). (D and E, upper panels). Comparison of H&E-staining of tamoxifen-treated control mice (WT) and Cre⁺<i>Cdh1</i>^fl/fl (KO) mice revealed a severe disruption of the epithelial architecture of small intestine (D) and colon (E). (D and E, bottom panels) Immunostaining for E-cadherin revealed a strong reduction in E-cadherin expression 6 days after start of recombination. Mean values and standard deviations are shown. Bars, 100 µm.</p

Impaired expression of E-cadherin results in elongation of crypts and villi.

<p>H&E staining of Cre⁺<i>Cdh1</i>^fl/fl (KO) and control mice (WT) on day 12 after induction of recombination on days 1, 2, 5, and 8, revealed milder changes in the epithelial architecture of small intestine (A) and colon (B) with elongation of crypts and disorganization of the cellular order. Immunostaining for E-cadherin revealed a reduction in E-cadherin expression 12 days after start of recombination in KO compared to WT mice in small intestine (C) and colon (D). Bars, 100 µm.</p

Induction of cell death and loss of adherens junctions and desmosomes upon loss of E-cadherin.

<p>(A and B) Immunostaining of small intestine (A) and colon (B) for cleaved caspase 3 in control (WT) and Cre⁺<i>Cdh1</i>^fl/fl (KO) mice treated with tamoxifen for 5 days was employed to identify apoptotic cells (arrowheads). (C) Quantitative analysis of apoptotic cells. 20 crypt-villus units in small intestine and 20 crypts in colon per animal were analyzed at the indicated time points (n = 4 mice/group). The rate of apoptotic cells is expressed as a percentage of total cell numbers and mean values and standard error means are shown (*, <i>P</i><0.005). (D) Transmission electron microscopy of the apical junctional complex of control (WT) and Cre⁺<i>Cdh1</i>^fl/fl (KO) mice. The intercellular space, microvilli (mv) and cellular substructures appeared unaltered. Compared to control mice, the junctional complex of Cre⁺<i>Cdh1</i>^fl/fl mice had preserved tight junctions (white arrowhead), but lacked adherens junctions with <i>rete terminale</i> (black arrowhead) and desmosomes (black arrow). Bars in A and C, 100 µm, in D 0.2 µm.</p

Impairment of bacterial defense in mice deficient for E-cadherin.

<p>Increase of bioluminescence in the Peyer's patches in Cre⁺<i>Cdh</i>1^fl/fl mice (A, right panel) compared to control mice (A, left panel) 5 days after oral infection with with 10⁹ CFU of bioluminescent <i>Yersinia enterocolitica</i>. Colonization of small intestine (B), and Peyer's Patches (C) of Cre⁺<i>Cdh1</i>^fl/fl and control mice (Cre⁺<i>Cdh1</i>^wt/fl). CFU for each mouse is shown and bars represent the median value. The limit of detection for yersiniae was 10 CFU for Peyer's Patches and 50 CFU for small intestine. Statistical significance is indicated by asteriks.</p