Project description:Paneth cells of intestinal crypts contribute to host defense by producing antimicrobial peptides that are packaged as granules for secretion into the crypt lumen. Here, we provide evidence using light and electron microscopy that postsecretory Paneth cell granules undergo limited dissolution and accumulate within the intestinal crypts of cystic fibrosis (CF) mice. On the basis of this finding, we evaluated bacterial colonization and expression of two major constituents of Paneth cells, i.e., {alpha}-defensins (cryptdins) and lysozyme, in CF murine intestine. Paneth cell granules accumulated in intestinal crypt lumens in both untreated CF mice with impending intestinal obstruction and in CF mice treated with an osmotic laxative that prevented overt clinical symptoms and mucus accretion. Ultrastructure studies indicated little change in granule morphology within mucus casts, whereas granules in laxative-treated mice appear to undergo limited dissolution. Protein extracts from CF intestine had increased levels of processed cryptdins compared with those from wild-type (WT) littermates. Nonetheless, colonization with aerobic bacteria species was not diminished in the CF intestine and oral challenge with a cryptdin-sensitive enteric pathogen, Salmonella typhimurium, resulted in greater colonization of CF compared with WT intestine. Modest downregulation of cryptdin and lysozyme mRNA in CF intestine was shown by microarray analysis, real-time quantitative PCR, and Northern blot analysis. Based on these findings, we conclude that antimicrobial peptide activity in CF mouse intestine is compromised by inadequate dissolution of Paneth cell granules within the crypt lumens. Total RNA was extracted from pooled small intestines of three WT and three CF mice using Tri-Reagent (Molecular Research Center, Cincinnati, OH), and poly(A) RNA was purified by using the MicroPoly(A) mRNA purification kit (Ambion, Austin, TX). The WT and CF poly(A) RNA samples were sent to IncyteGenomics (St. Louis, MO) where they were labeled with cyanine 3 (Cy3) and Cy5, respectively, and hybridized with the UniGEM1.31 array representing 9,570 known genes and expressed sequence tags.

Project description:Background: Cystic fibrosis (CF) is caused by mutations in the CFTR gene that impair function of this cAMP-regulated Cl- channel. In the small intestine, loss of CFTR function creates a dehydrated, acidic luminal environment which is believed to cause an accumulation of mucus, a phenotype characteristic of CF. CF mice have an innate immune response and impaired intestinal transit as well. We investigated whether lubiprostone, which activates the CLC2 Cl- channel, would improve the CF intestinal phenotype. Methods: Cftrtm1UNC (CF) and wildtype (WT) littermate mice on the C57BL/6 background were used. Lubiprostone (10ug/kg-day) was administered by gavage for two weeks. Mucus accumulation was estimated from crypt lumen widths in Carnoy's-fixed, PAS/AB stained sections. Luminal bacterial load was measured by qPCR for the bacterial 16S gene. Gastric emptying and small intestinal transit were assessed by gavage of rhodamine dextran. Gene expression was evaluated by Affymetrix Mouse430 2.0 microarray. Results: Crypt width in control CF mice was 700% that of WT mice (P<0.001). Lubiprostone did not affect WT crypt width but, unexpectedly, increased CF crypt width 22% (P=0.001). Lubiprostone increased bacterial load in WT mice to 490% of WT control levels (P=0.008). Conversely, lubiprostone decreased bacterial overgrowth in CF mice by 60% (P=0.005). Lubiprostone significantly increased gastric emptying at 20 min postgavage in both WT (P<0.001; control=57±3%, treated=81±4%) and CF mice (P<0.001; control=48±4%, treated=75±5%). After lubiprostone small intestinal transit was significantly enhanced in WT mice (P=0.024) but the effect was not significant in CF mice (P=0.377). Among other innate immune markers, expression of mast cell genes was elevated ~20-fold in the control CF intestine and lubiprostone decreased expression to WT control levels. Conclusions: These results indicate that lubiprostone has some benefits for the CF intestinal phenotype, especially on bacterial overgrowth and the innate immune response. The unexpected observation of increased mucus accumulation in the crypts of lubiprostone-treated CF mice suggests the possibility that lubiprostone increases mucus secretion. For each group (control wild type, lubiprostone-treated wild type, contol Cftr null, and lubiprostone-treated cftr null), equal amounts of total RNA extracted from the entire small intestine were pooled for analysis.

Project description:Background: Cystic fibrosis (CF) is caused by mutations in the CFTR gene that impair function of this cAMP-regulated Cl- channel. In the small intestine, loss of CFTR function creates a dehydrated, acidic luminal environment which is believed to cause an accumulation of mucus, a phenotype characteristic of CF. CF mice have an innate immune response and impaired intestinal transit as well. We investigated whether lubiprostone, which activates the CLC2 Cl- channel, would improve the CF intestinal phenotype. Methods: Cftrtm1UNC (CF) and wildtype (WT) littermate mice on the C57BL/6 background were used. Lubiprostone (10ug/kg-day) was administered by gavage for two weeks. Mucus accumulation was estimated from crypt lumen widths in Carnoy's-fixed, PAS/AB stained sections. Luminal bacterial load was measured by qPCR for the bacterial 16S gene. Gastric emptying and small intestinal transit were assessed by gavage of rhodamine dextran. Gene expression was evaluated by Affymetrix Mouse430 2.0 microarray. Results: Crypt width in control CF mice was 700% that of WT mice (P<0.001). Lubiprostone did not affect WT crypt width but, unexpectedly, increased CF crypt width 22% (P=0.001). Lubiprostone increased bacterial load in WT mice to 490% of WT control levels (P=0.008). Conversely, lubiprostone decreased bacterial overgrowth in CF mice by 60% (P=0.005). Lubiprostone significantly increased gastric emptying at 20 min postgavage in both WT (P<0.001; control=57±3%, treated=81±4%) and CF mice (P<0.001; control=48±4%, treated=75±5%). After lubiprostone small intestinal transit was significantly enhanced in WT mice (P=0.024) but the effect was not significant in CF mice (P=0.377). Among other innate immune markers, expression of mast cell genes was elevated ~20-fold in the control CF intestine and lubiprostone decreased expression to WT control levels. Conclusions: These results indicate that lubiprostone has some benefits for the CF intestinal phenotype, especially on bacterial overgrowth and the innate immune response. The unexpected observation of increased mucus accumulation in the crypts of lubiprostone-treated CF mice suggests the possibility that lubiprostone increases mucus secretion.

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Paneth cell granule dissolution and bacterial colonization in the intestine of CF mice

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