Intestinal Mucosa

The effect of 5-aminoimidazole-4-carboxamide-ribonucleoside (AICAR) activation of the AMP-activated protein kinase (AMPK) on the transport of the model radiolabeled dipeptide [3H]-D-Phe-L-Gln was investigated in the human epithelial colon cancer cell line Caco-2. Uptake and transepithelial fluxes of [3H]-D-Phe-L-Gln were carried out in differentiated Caco-2 cell monolayers, and hPepT1 and glucose transporter 2 (GLUT2) protein levels were quantified by immunogold electron microscopy. AICAR treatment of Caco-2 cells significantly inhibited apical [3H]-D-Phe-L-Gln uptake, matched by a decrease in brush-border membrane hPepT1 protein but with a concomitant increase in the facilitated glucose transporter GLUT2. A restructuring of the apical brush-border membrane was seen by electron microscopy. The hPepT1-mediated transepithelial (A-to-B) peptide flux across the Caco-2 monolayers showed no significant alteration in AICAR-treated cells. The electrical resistance in the AICAR-treated monol...

To understand the interactions between iron and zinc during absorption in iron- and zinc-deficient rats, and their consequences on intestinal oxidant-antioxidant balance. Twenty-four weanling Wistar-Kyoto rats fed an iron- and zinc-deficient diet (< 6.5 mg Fe and 4.0 mg Zn/kg diet) for 4 wk were randomly divided into three groups (n = 8, each) and orally gavaged with 4 mg iron, 3.3 mg zinc, or 4 mg iron + 3.3 mg zinc for 2 wk. At the last day of repletion, 3 h before the animals were sacrificed, they received either 37 mBq of (55)Fe or (65)Zn, to study their localization in the intestine, using microautoradiography. Hemoglobin, iron and zinc content in plasma and liver were measured as indicators of iron and zinc status. Duodenal sections were used for immunochemical staining of ferritin and metallothionein. Duodenal homogenates (mitochondrial and cytosolic fractions), were used to assess aconitase activity, oxidative stress, functional integrity and the response of antioxidant e...

The goal of this study was to evaluate the influence of severe protein-energy malnutrition (PEM) on lipid composition and fatty acid profile in the small intestinal mucosa of lactating pigs. Malnutrition was achieved by 80% protein-energy restriction for 30 d (20% of the food intake in the control group) in 7-d-old newborn piglets. Malnourished piglets had significantly lower concentrations of cholesterol, phospholipid and triglycerides in the jejunum and ileum compared with freely fed controls. Fatty acid composition of the intestinal mucosa was severely affected by malnutrition. A sharp decline in the relative percentages of (n-3) and (n-6) long-chain polyunsaturated fatty acids (LC-PUFA) in malnourished piglets paralleled higher (n-9) fatty acid proportions in the total mucosa, microsomes and phospholipids of the jejunum. The structure of the small intestine was severely affected as assessed by light and electron microscopy, and alkaline phosphatase and disaccharidase activities ...

A histological study was undertaken to determine the efficiency in the removal of the mucosa and Peyer's patches by standard processing of bovine intestines into natural sausage casings. The second objective was to calculate the quantity of lymphoid and nervous tissue per consumable sausage. For the histological analysis, intestinal samples were collected from 80 beef cattle during the slaughter process. Fresh and cleaned intestines were compared in analyzing the thickness of the intestinal wall, weight reduction during cleaning, removal of the mucosal layer, and the presence of lymphoid and neural tissue after cleaning. The obtained data indicate a weight reduction of about 50% during standard cleaning procedures, as 90% of the mucosa and 48% of the lymphoid tissue are removed. Based on the quantitative histological image analysis, it was calculated that 1 m of cleaned casings, weighing on average 64 g, contains about 2.8 g of mucosa, 0.3 g of lymphoid tissue, and 0.1 g of neur...

Previous studies have shown that high concentrations of ethanol (≥40%) cause functional damage of the gastrointestinal epithelial barrier by direct cytotoxic effect on the epithelial cells. The effects of lower noncytotoxic doses of ethanol on epithelial barrier function are unknown. A major ...

Background: Folate deficiency is common in alcoholic patients, in part due to abnormal transport across membranes relevant to folate homeostasis. The reduced folate carrier (RFC) transports monoglutamyl folates across tissue membranes and could be affected by chronic exposure to ethanol. The micropig model is suitable to study the effect of alcoholism on RFC and folate transport across membranes.Methods: The membrane transport of [3H]-folic acid was measured by a vacuum filtration method in jejunal brush border (JBB), liver plasma membrane (LPM), and kidney brush border (KBB) membranes vesicles from micropigs fed control or 40% ethanol diets for 12 months. RFC transcripts were analyzed by reverse transcription polymerase chain reaction in jejunal mucosa, liver, and kidney from the same animals.Results: When we compared results from three relevant membranes in control animals, the transport of [3H]-folic acid was highest in LPM, 3-fold lower in KBB (p < 0.001), and 6-fold lower in JBB (p < 0.001). The concentration of RFC transcripts per total RNA was greatest in liver, followed by kidney and jejunum. The transport of [3H]-folic acid by JBB vesicles from chronic ethanol-fed animals exhibited 2-fold lower Km and Vmax (p < 0.05), whereas there was no ethanol effect on the Vmax of [3H]-folic acid transport by LPM or KBB. RFC transcript levels were 10-fold lower in jejunal mucosa from ethanol-fed animals than in control-fed animals (p < 0.005).Conclusions: Although our findings demonstrate different RFC transcript amounts and transport efficiencies among tissues, the present studies suggest that chronic ethanol exposure decreases the intestinal absorption of folic acid by altering the expression of RFC and consequently its transport kinetics in JBB. These findings provide a mechanism for the clinical finding of reduced folic acid absorption in chronic alcoholics.

Phosphorylation of the transcriptional coactivator YAP1 is a key event in defining Hippo signaling outputs. Previous studies demonstrated that phosphorylation of YAP1 at serine 127 (S127) sequesters YAP1 in the cytoplasm and consequently inhibits YAP1 transcriptional activity. Mammalian tissue-culture experiments suggest that downstream of MST1/2 signaling, LATS1/2 function as YAP1-S127 kinases. However, studies of Mst1/2 knockout mouse models revealed that the identity of the physiological YAP1-S127 kinase(s) in certain tissues, such as the intestine, remains unknown. We show that mammalian NDR1/2 kinases phosphorylate YAP1 on S127 and thereby negatively regulate YAP1 activity in tissue-cultured cells. By studying NDR1/2-deficient mice, we demonstrate the in vivo relevance of NDR1/2-mediated regulation of YAP1. Specifically, upon loss of NDR1/2 in the intestinal epithelium, endogenous S127 phosphorylation is decreased whereas total YAP1 levels are increased. Significantly, ablation...

A sucrose-rich diet has repeatedly been observed to have cocarcinogenic actions in the colon and liver of rats and to increase the number of aberrant crypt foci in rat colon. To investigate whether sucrose-rich diets might directly increase the genotoxic response in the rat colon or liver, we have added sucrose to the diet of Big Blue rats, a strain of Fischer rats carrying 40 copies of the lambda-phage on chromosome 4. Dietary sucrose was provided to the rats for 3 weeks at four dose levels including the background level in the purified diet [3.4% (control), 6.9%, 13.8%, or 34.5%] without affecting the overall energy and carbohydrate intake. We observed a dose-dependent increase in the mutation frequency at the cII site in the colonic mucosa with increased sucrose levels, reaching a 129% increase at the highest dose level. This would indicate a direct or indirect genotoxic effect of a sucrose-rich diet. No significant increase in mutations was observed in the liver. To seek an expl...

The increasing use of nanomaterials in healthcare and industrial products heightens the possibility of their ingestion by humans, other mammals, and fish. While toxicity of many nanomaterials has recently been studied, reports of non-lethal effects of nanomaterials remain ill-defined. This study investigates possible pathways by which nanoparticles, titanium dioxide (TiO(2)), could cross the epithelium layer by employing both toxicity and mechanistic studies. This study provides evidence that at 10 microg/mL and above, TiO(2) nanoparticles cross the epithelial lining of the intestinal model by transcytosis, albeit at low levels. TiO(2) was able to penetrate into and through the cells without disrupting junctional complexes, as measured by gamma-catenin. To monitor the epithelial integrity, transepithelial electrical resistance (TEER) was employed and determined low concentrations (10 or 100 microg/mL) of TiO(2) do not disrupt epithelial integrity. Live/dead analysis results did not ...

Background & Aims: There is mounting evidence that matrix metalloproteinases are the predominant proteinases expressed in the gut mucosa during active inflammatory bowel disease. We investigated the role of metalloproteinase 9 (MMP-9), a secreted gelatinase that is consistently up-regulated in both animal models and human inflammatory bowel disease and is associated with disease severity, in the pathogenesis of colitis by using mice containing a targeted deletion of the MMP-9 gene. Methods: Dextran sodium sulfate–induced colitis and Salmonella typhimurium–induced enterocolitis were used as animal models to study colitis. Results: MMP-9 activity and protein expression were absent from normal colonic mucosa but were up-regulated during experimental colitis. MMP-9−/− mice exposed to dextran sodium sulfate or salmonella had a significantly reduced extent and severity of colitis. Immunohistochemical studies showed that MMP-9 was localized to epithelial cells and granulocytes during active colitis. The immune response to systemic administration of Salmonella typhimurium was not affected in MMP-9−/− mice. Neutrophil transmigration studies and bone marrow chimeras showed that neutrophil MMP-9 is neither required for its migration nor sufficient to induce tissue damage during colitis and that epithelial MMP-9 is important for tissue damage. MMP-9 inhibited cell attachment and wound healing in the model intestinal epithelial cell line, Caco2-BBE. Conclusions: Taken together, our data suggest that MMP-9 expressed by epithelial cells may play an important role in the development of colitis by modulating cell–matrix interaction and wound healing. Thus, strategies to inhibit MMP-9 may be of potential therapeutic benefit.

Malignancies arising from biliary tract epithelia, or cholangiocarcinoma, are rare tumors that have a poor prognosis. The incidence of these tumors is gradually increasing in many countries. Recent advances have been made in identifying some of the risk factors, and the need for appropriate classification is emerging. The diagnosis of cholangiocarcinoma is often difficult and requires multiple complementary studies. The use of molecular approaches may improve the diagnostic utility of biliary cytology. Treatment of these tumors is complex, and there are many different treatment options. Although surgical resection can be curative, many patients with cholangiocarcinoma are diagnosed at an advanced stage when only palliative approaches can be used. Photodynamic therapy is emerging as a useful modality.