Modulation of intracellular growth of Listeria monocytogenes in human enterocyte Caco-2 cells by interferon-gamma and interleukin-6: role of nitric oxide and cooperation with antibiotics.
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The influence of interferon (IFN)-gamma and interleukin (IL)-6 on the intracellular growth of Listeria monocytogenes phagocytosed from the apical pole was examined in polarized Caco-2 cells. IFN-gamma (from the apical pole) and IL-6 (from the basolateral pole) considerably reduced the bacterial intracellular growth, an effect largely abolished by l-monomethyl arginine. Both cytokines caused overexpression of inducible nitric oxide synthase. IL-6, but not IFN-gamma, caused a partial restriction of L. monocytogenes in phagosomes and largely prevented the cytosolic forms from being surrounded by actin. Ampicillin was bacteriostatic in unstimulated cells but modestly bactericidal in cells treated with IFN-gamma and IL-6. Azithromycin (a macrolide) was fairly bactericidal and sparfloxacin (a fluoroquinolone) highly bactericidal in all situations. IFN-gamma and IL-6 may therefore be important determinants in the protection of epithelial cells from intracellular multiplication of L. monocytogenes. Ampicillin may fail in their absence, requiring the use of other antibiotics such as the fluoroquinolones. (+info)
Intestinal adaptation and enterocyte apoptosis following small bowel resection is p53 independent.
(2/903)
Adaptation following small bowel resection (SBR) signals enterocyte proliferation and apoptosis. Because p53-induced p21(waf1/cip1) may be important for apoptosis in many cells, we hypothesized that these genes are required for increased enterocyte apoptosis during adaptation. Male C57BL/6 (wild-type) or p53-null mice underwent 50% proximal SBR or sham operation (bowel transection-reanastomosis). Adaptation (DNA-protein content, villus height-crypt depth, enterocyte proliferation), appearance of apoptotic bodies, and p53 and p21(waf1/cip1) protein expression were measured in the ileum after 5 days. Adaptation was equivalent after SBR in both wild-type and p53-null mice as monitored by significantly increased ileal DNA-protein content, villus height, and enterocyte proliferation. The number of crypt apoptotic bodies increased significantly after SBR evenly in both wild-type and p53-null mice. In the p53-null mice, SBR substantially induced the expression of p21(waf1/cip1) protein in villus enterocytes. The p53-independent induction of p21(waf1/cip1) may account for the similar intestinal response to SBR between wild-type and p53-null mice. Intestinal adaptation and increased enterocyte apoptosis following intestinal resection occur via a p53-independent mechanism. (+info)
Increased dietary triacylglycerol markedly enhances the ability of isolated rabbit enterocytes to secrete chylomicrons: an effect related to dietary fatty acid composition.
(3/903)
Dietary fats are efficiently absorbed in the small intestine and transported into the blood via the lymph as chylomicrons, despite enormous variations in the amount and composition of the dietary lipid. The aim of the present study was to investigate how enterocytes respond to increased dietary fats of different composition. Rabbits were fed a low fat chow diet, and chow supplemented with sunflower oil (high n-6 polyunsaturated fatty acids), fish oil (high n-3 polyunsaturated fatty acids), or an oil mixture of a composition similar to that of the typical western diet. Feeding fat for 2 weeks markedly stimulated the ability of the isolated enterocytes to synthesize and secrete apolipoprotein B48, triacylglycerol, and cholesteryl ester (up to 18-, 50-, and 80-fold, respectively) in particles of chylomicron density. The magnitude of stimulation was sunflower oil > western diet lipid > fish oil. Single doses of lipid given 18 h prior to isolation of enterocytes stimulated chylomicron secretion by only 10% of that observed after 2 weeks of dietary supplementation. Enterocytes are replaced rapidly (half-life 1-2 days) by cells which move from the crypts to the tips of the villi, where absorption of nutrients takes place. Our observations suggest that dietary lipids modulate the function of enterocytes as they move from the crypts, so that the cells are 'turned-on' to lipid absorption. The results also show that diets of different fatty acid composition vary in their effects. (+info)
Regulation of small intestinal Na-P(i) type IIb cotransporter by dietary phosphate intake.
(4/903)
Dietary restriction of phosphate is a well-known stimulator (acting indirectly via vitamin D(3)) of small intestinal apical Na-P(i) cotransport. In the present study, we document by Western blots and immunohistochemistry that, in mice, a low-P(i) diet given for several days leads (in parallel to a stimulation of Na-P(i) cotransport) to an increase of the abundance of the type IIb Na-P(i) cotransporter in the brush-border membrane of mouse enterocytes. Similar results were also obtained by an injection of cholecalciferol. The abundance of the type IIb transcript was investigated by Northern blots. These results indicated that the amount of the type IIb transcript was not changed by either low-P(i) diet or cholecalciferol. It is concluded that stimulation of intestinal Na-P(i) cotransport by low-P(i) diet and vitamin D(3) can be explained by an increased amount of type IIb Na-P(i) cotransporters in the brush-border membrane and that augmentation of type IIb Na-P(i) cotransporters is not related to an increased rate of transcription of the type IIb gene. (+info)
Identification of the major intestinal fatty acid transport protein.
(5/903)
While intestinal transport systems for metabolites such as carbohydrates have been well characterized, the molecular mechanisms of fatty acid (FA) transport across the apical plasmalemma of enterocytes have remained largely unclear. Here, we show that FATP4, a member of a large family of FA transport proteins (FATPs), is expressed at high levels on the apical side of mature enterocytes in the small intestine. Further, overexpression of FATP4 in 293 cells facilitates uptake of long chain FAs with the same specificity as enterocytes, while reduction of FATP4 expression in primary enterocytes by antisense oligonucleotides inhibits FA uptake by 50%. This suggests that FATP4 is the principal fatty acid transporter in enterocytes and may constitute a novel target for antiobesity therapy. (+info)
Binding of pili from uropathogenic Escherichia coli to membranes secreted by human colonocytes and enterocytes.
(6/903)
PapG adhesins mediate the binding of uropathogenic Escherichia coli. Although receptors for these adhesins have not been demonstrated in intestinal epithelia, the colonic microflora includes strains of uropathogenic E. coli. We now report that surfactant-like particles secreted by the human intestine contain receptors for PapG adhesins and may provide an intestinal habitat for uropathogenic bacteria. (+info)
Up-regulation of glutathione S-transferase activity in enterocytes of young children.
(7/903)
The relationship between age and busulfan apparent oral clearance (Cl/F) expressed relative to adjusted ideal body weight and body surface area (bsa) was evaluated in 135 children aged 0 to 16 years undergoing hematopoietic stem cell transplantation for various disorders. Busulfan plasma levels were measured by gas chromatography-mass spectrometry after the first daily dose of the 4-day dosing regimen. Cl/F expressed relative to adjusted ideal body weight (ml/min/kg) and bsa (ml/min/m(2)) was lower in 9- to 16-year-old (y.o.) compared with 0- to 4-y.o. children (49 and 30%; p<.001). We hypothesized that the greater busulfan Cl/F observed in young children was in part due to enhanced (first-pass intestinal) metabolism. Busulfan conjugation rate was compared in incubations with human small intestinal biopsy specimens from healthy young (1- to 3-y.o.) and older (9- to 17-y.o.) children. Villin content in biopsy specimens was determined by Western blot and busulfan conjugation rate was expressed relative to villin content to control for differences in epithelial cell content in pinch biopsies. Intestinal biopsy specimens from young children had a 77% higher busulfan conjugation rate (p =.037) compared with older children. We have previously shown that glutathione-S-transferase (GST) A1-1 is the major isoform involved in busulfan conjugation, and that this enzyme is expressed uniformly along the length of adult small intestine. Thus, the greater busulfan conjugation activity in intestinal biopsies of the young children was most likely due to enhanced GSTA1-1 expression. We conclude that age dependence in busulfan Cl/F appears to result at least in part from enhanced intestinal GSTA1-1 expression in young children. (+info)
NOX, a novel nitric oxide scavenger, reduces bacterial translocation in rats after endotoxin challenge.
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Endotoxemia promotes gut barrier failure and bacterial translocation (BT) by upregulating inducible nitric oxide synthase (iNOS) in the gut. We hypothesized that administration of a dithiocarbamate derivative, NOX, which scavenges nitric oxide (NO), may reduce intestinal injury and BT after lipopolysaccharide (LPS) challenge. Sprague-Dawley rats were randomized to receive NOX or normal saline via subcutaneously placed osmotic pumps before or after LPS challenge. Mesenteric lymph nodes, liver, spleen, and blood were cultured 24 h later. Transmucosal passage of Escherichia coli C-25 or fluorescent beads were measured in an Ussing chamber. Intestinal membranes were examined morphologically for apoptosis, iNOS expression, and nitrotyrosine immunoreactivity. NOX significantly reduced the incidence of bacteremia, BT, and transmucosal passage of bacteria and beads when administered before or up to 12 h after LPS challenge. LPS induced enterocyte apoptosis at the villus tips where bacterial entry was demonstrated by confocal microscopy. NOX significantly decreased the number of apoptotic nuclei and nitrotyrosine residues. NOX prevents LPS-induced gut barrier failure by scavenging NO and its toxic derivative, peroxynitrite. (+info)