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At least 19 recordsLinked to original sources
PubMed1984

Positional dependence of enterocyte membrane potential in hamster and rabbit enterocytes.

A technique is described allowing microelectrode impalement of enterocytes located at known positions along intestinal villi from rabbits and hamsters. Using this technique a 5 mV hyperpolarization in membrane potential is shown to occur as enterocytes migrate over the basal third of intestinal villi. The villus structure of the hamster ileum is similar to the rabbit, but the enterocyte lifespan in these two tissues differs considerably (enterocyte migration rates of 17.6 and 6.3 microns hr-1 for hamster and rabbit respectively). A correlation was found between the position an enterocyte occupied on the crypt-villus axis and the developmental state of the membrane potential. No such correlation existed when making comparisons on a time basis. These results are discussed both in terms of what is now known concerning different aspects of enterocyte development and in relation to what type of control mechanism might be generally responsible for initiating differentiation in this tissue.

Animals↗
PubMed2001

The impact of P-glycoprotein efflux on enterocyte residence time and enterocyte-based metabolism of verapamil.

P-glycoprotein (P-gp) can limit the intestinal permeability of a number of compounds and may therefore influence their exposure to metabolizing enzymes within the enterocyte (e.g. cytochrome P450 3A, CYP 3A). In this study, the intestinal metabolic profile of verapamil, the influence of P-gp anti-transport on the cellular residence time of verapamil, and the impact of this change in residence time on the extent of enterocyte-based metabolism have been investigated in-vitro, utilizing segments of rat jejunum and side-by-side diffusion chambers. Verapamil exhibited concentration-dependent P-gp efflux and CYP 3A metabolism. The P-gp efflux of verapamil (1 microM) increased the cellular residence time across the intestinal membrane (approximately 3-fold) in the mucosal to serosal (m to s) direction relative to serosal to mucosal (s to m), yielding significantly greater metabolism (approximately 2-fold), presumably as a result of the prolonged exposure to CYP 3A. Intestinal metabolism of verapamil generated not only norverapamil, but resulted also in the formation of an N-dealkylated product (D-617). Norverapamil and D-617 accumulated significantly in mucosal chambers, relative to serosal chambers, over the time course of the experiment. Based on these in-vitro data, it was apparent that P-gp efflux prolonged the cellular residence time of verapamil (m to s) and therefore increased the extent of intestinal metabolism, and also played a role in metabolite secretion from within the enterocyte.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1980

Simultaneous isolation of brush border and basolateral membrane from rabbit enterocytes. Presence of brush border hydrolases in the basolateral membrane of rabbit enterocytes.

By a slight modification of the procedure described by Gratecos et al. (Gratecos, D., Knibiehler, M., Benoit, V. and Sémériva, M. (1978) Biochim. Biophpys. Acta 512, 508-524), the basolateral and brush border membranes of rabbit enterocytes have been purified concomitantly from the same aliquot of mucosa. The two types of membrane have been obtained with the same yield (15%) and enrichment of specific markers (18-fold). The presence in the basolateral membrane of hydrolases known to be specific of the brush border membrane has been confirmed by using immunological techniques.

Animals↗
PubMed1994

Bacterial translocation across enterocytes: results of a study of bacterial-enterocyte interactions utilizing Caco-2 cells.

Due to the inherent limitations of in vivo studies, the cellular mechanisms underlying the process of bacterial translocation (BT) across the intestinal epithelial barrier are poorly understood. Thus, we have utilized the Caco-2 intestinal cell line to study this process. Caco-2 cells were grown to confluence on semipermeable membranes contained in the upper compartment of a 2 compartment system. Cellular confluence and tight junction integrity was verified by measurements of the transepithelial electrical resistance in ohms cm2.BT was measured by culturing the bacteria (nonpathogenic Escherichia coli) that were able to cross the Caco-2 monolayer and were present in the bottom compartment, as well as by monitoring the passage of 1-micron fluorescent beads. Caco-2 cells were pretreated with several metabolic inhibitors: 1.0 mM sodium azide (oxidative phosphorylation), 10 micrograms/ml nocodazole (microtubule), 10 microM phalloidine (microfilament), and 5.0 micrograms/ml cytochalasin D (microfilament). To investigate the mechanisms of BT. Both bacteria and fluorescent beads crossed the Caco-2 monolayer. Azide had no effect on BT, while both nocodazole (n = 17) and phalloidine (n = 14) significantly decreased translocation of E. coli versus control monolayers (p < .05). Cytochalasin D increased BT versus control membranes, however this was associated with loss of tight junction integrity (transepithelial electrical resistance decreased from 201 +/- 79 to 87 +/- 6.4). BT across Caco-2 cells appears to be a polar process which is to some extent microtubule- and microfilament-dependent.

Azides↗
PubMed2001

Integrin expression, enterocyte maturation, and bacterial internalization.

BACKGROUND: Little is known about the molecular mechanisms involved in the translocation of enteric bacteria. Adhesion molecules mediate interactions between some enteric pathogens and mammalian cells, but no such interactions have been identified for enterocytes and normal enteric bacteria. Using enteric pathogens, adhesion molecule expression has been linked to bacterial internalization and to enterocyte differentiation. Therefore, experiments were designed to study enterocyte integrin expression and differentiation, as well as enterocyte internalization of Salmonella typhimurium, Proteus mirabilis, and Escherichia coli. MATERIALS AND METHODS: Relative expression of the alpha2, alpha3, and beta1 integrin subunits on Caco-2 and HT-29 enterocytes (mature and immature) was measured by ELISA. Bacteria-enterocyte surface interactions were observed by light and scanning electron microscopy. Bacterial internalization by enterocytes was quantified using the gentamicin protection assay. RESULTS: Expression of the alpha2, alpha3, and beta1 integrin subunits was consistently increased in immature compared to mature Caco-2 enterocytes; however, compared to mature enterocytes, immature HT-29 enterocytes had similar expression of alpha3 and beta1 but decreased alpha2. Compared to untreated mature enterocytes, bacterial internalization was increased in immature enterocytes as well as mature enterocytes with lateral membranes artifactually exposed. However, there was no difference in bacterial internalization between immature enterocytes and mature enterocytes treated to expose the lateral membrane. CONCLUSIONS: Bacterial internalization by enterocytes appeared to be due to factors other than integrin expression or enterocyte differentiation. Exposure of the lateral enterocyte membrane may play an important role in facilitating bacterial internalization by enterocytes.

Antigens, CD↗
PubMed1996

Effect of hypoxia on enterocyte endocytosis of enteric bacteria.

OBJECTIVE: To clarify the effect of hypoxia on bacteria-enterocyte interactions. DESIGN: Randomized. SETTING: Research laboratory. SUBJECTS: Enteric bacterial and cultured human intestinal epithelial cells, HT-29 cells. INTERVENTIONS: The effect of hypoxia on bacterial internalization and intracellular survival was studied, using enterocytes cultured for 21 days in either 20%, 10%, or 5% oxygen. The effect of bacterial growth conditions on bacterial internalization by enterocytes was studied, using bacterial cells in either the log phase or stationary phase of aerobic growth, and using bacterial cells in stationary phase, grown either under low oxygen conditions or under anaerobic conditions. MEASUREMENTS AND MAIN RESULTS: Individual strains of enteric bacteria were incubated with HT-29 cells for 1 hr. Numbers of internalized bacteria were subsequently quantified after enterocyte lysis. Bacterial growth conditions (anaerobic vs. aerobic and log-phase vs. stationary-phase bacterial cells) had no noticeable effect on the numbers of Salmonella typhimurium, Proteus mirabilis, and Escherichia coli internalized by enterocytes. Enterocytes cultivated in 20%, 10%, or 5% oxygen were >95% viable. Enterocytes cultivated in 20% oxygen were confluent, but those enterocytes cultivated in hypoxia were not confluent and were fewer in number compared with enterocytes cultivated in normoxia. Compared with enterocytes grown in normoxia, enterocytes cultivated in 5% and 10% oxygen internalized greater numbers of each of seven strains of enteric bacteria, including Listeria monocytogenes (two strains), Enterococcus faecalis (two strains), and P. mirabilis, E. coli (two strains), with statistically significant increases noted for five of these seven bacterial strains. Intracellular survival of L. monocytogenes and P. mirabilis was assayed. Both species survived intracellularly for 22 hrs, with no noticeable differences in the numbers of intracellular bacteria recovered from enterocytes cultivated in 20%, 10%, and 5% oxygen. CONCLUSION: These in vitro results suggest that augmented bacterial endocytosis by enterocytes might at least partially explain the increased frequency of bacterial translocation associated with tissue ischemia.

Bacterial Translocation↗
PubMed1996

Intracellular survival of enteric bacteria in cultured human enterocytes.

Translocating enteric bacteria have been visualized within intact intestinal epithelial cells in animal models of bacterial translocation. Although the ability of the enterocyte to engulf bacteria has been well documented in both in vivo and in vitro experimental models, relatively little is known about the enterocyte's ability to degrade internalized bacteria. Intracellular survival of eight strains of enteric bacteria (two strains of Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, two strains of Escherichia coli, and two strains of Enterococcus faecalis) was quantified over a 20 h period using two different types of terminally differentiated polarized enterocytes considered relevant in vitro models of human small intestinal epithelium, namely Caco-2 and HT-29 cells. Caco-2 enterocytes were generally more permissive for bacterial uptake when compared with HT-29 enterocytes. However, bacterial survival was similar within each type of enterocyte, and most strains of enteric bacteria remained viable within enterocytes for the 20 h duration of the assay. In addition, with the exception of one strain of L. monocytogenes in Caco-2 cells, intracellular enteric bacteria had no noticeable effect on host enterocyte viability for this 20 h duration. Transmission electron microscopy was used to visualize both intact and degraded bacteria within individual enterocytes, suggesting that prolonged bacterial survival might have resulted from simultaneous bacterial degradation and replication. Thus, although enterocytes internalize enteric bacteria, enterocytes might not kill internalized bacteria as efficiently as leukocytes. Observations of bacterial intracellular survival supported the hypothesis that the enterocyte might be a portal of entry for translocating microbes, and observations of intracellular bacterial degradation might have implications for the role of the enterocyte as an antigen-presenting cell.

Caco-2 Cells↗
PubMed1998

Shigella dysenteriae type 1 toxin induced lipid peroxidation in enterocytes isolated from rabbit ileum.

To evaluate the role of reactive oxygen species (ROS) in Shigella dysenteriae 1 toxin (STx) mediated intestinal infection, the ligated rabbit small intestinal loops were injected with STx. The enterocytes isolated from STx treated rabbit ileal loops had a significantly higher level of lipid peroxidation as compared to enterocytes isolated from control rabbit ileum. To study the role of second messengers in STx mediated intestinal damage, the in vivo and in vitro effects of modulators of lipid peroxidation of enterocytes were used. The presence of Ca2+-ionophore A23187 enhanced the extent of lipid peroxidation in enterocytes isolated from the control and STx treated rabbit ileum. However, 1-verapamil only marginally decreased the lipid peroxidation level of enterocytes isolated from STx treated rabbit ileum. The in vitro effect of modulators was in agreement with in vivo studies. Dantrolene significantly decreased the extent of lipid peroxidation of enterocytes isolated from STx treated rabbit ileum. PMA significantly increased the lipid peroxidation level of enterocytes isolated from control ileum. However, PMA could not further enhance the lipid peroxidation level of enterocytes isolated from STx treated rabbit ileum. The presence of H-7 significantly decreased the extent of lipid peroxidation of enterocytes isolated from STx treated rabbit ileum. In vitro effect of PMA and H-7 was in agreement with that of in vivo findings. The role of arachidonic acid metabolites, prostaglandins (PGs), in mediating STx induced lipid peroxidation was also studied. The presence of indomethacin (a PG synthesis inhibitor) significantly decreased the lipid peroxidation induced by STx. These findings suggest that lipid peroxidation induced by STx is mediated through cytosolic calcium. The increase in (Ca2+)i leads to activation of PKC. A significant decrease in the enterocyte levels of antioxidant enzymes superoxide dismutase, catalase and reduced glutathione in STx treated rabbit ileum as compared to control was seen. A significant decrease in vitamin E levels was also observed. This suggests that there is decreased endogenous intestinal protection against ROS in STx mediated intestinal infection which could contribute to enterocyte membrane damage that ultimately leads to changes in membrane permeability and thus to fluid secretion.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1999

Iron proteins of duodenal enterocytes isolated from mice with genetically and experimentally altered iron metabolism.

The molecular basis for the control of iron absorption by the duodenum remains unknown: however, ferritin (Ft) and the iron status of enterocytes have been suggested as regulatory factors. We determined the iron and Ft status of duodenal enterocytes from mice with hypotransferrinaemia, a genetic defect leading to greatly enhanced iron absorption, and for comparison we also investigated mice with experimentally-altered iron absorption. Duodenal enterocytes were isolated and analysed for Ft and non-haem iron content and for transferrin binding (as a measure of transferrin receptor activity). RNA was extracted from the duodenal mucosa and examined for transferrin receptor and H- and L-Ft mRNA levels by Northern hybridization analysis. Ft levels were elevated in enterocytes of hypotransferrinaemic mice, similar to that seen in iron dextran-injected mice of the CD1-strain. Enterocyte Ft levels were reduced in mice fed a diet diminished in iron, but unchanged in hypoxic mice enterocytes. Enterocytes of hypotransferrinaemic mice had normal non-haem iron levels and transferrin binding; however, enterocytes from CD-1 mice fed a low iron diet had increased transferrin binding and a decreased non-haem iron content. Duodenal mRNA levels for transferrin receptor and H-Ft were unchanged in hypotransferrinaemic mice, whereas L-Ft was increased. We conclude from the Ft and non-haem iron contents and transferrin binding that duodenal enterocytes from hypotransferrinaemic mice are not simply iron deficient, leading to increased expression of iron carriers proteins. Duodenal iron absorption can be enhanced in mice even when enterocyte Ft levels are raised or unchanged, suggesting that iron absorption is regulated by developmentally programmed expression of iron transporters by enterocytes.

Animals↗
PubMed1996

Bacteroides fragilis enterotoxin modulates epithelial permeability and bacterial internalization by HT-29 enterocytes.

BACKGROUND & AIMS: Enterotoxigenic Bacteroides fragilis has been associated with diarrheal disease, and the enterotoxin has a cytopathic effect on cultured HT-29 enterocytes. Experiments were designed to determine the effect of B. fragilis enterotoxin on bacteria-enterocyte interactions. METHODS: Confluent HT-29 enterocytes were incubated for 1 hour with B. fragilis enterotoxin, followed by 1 hour of incubation with pure cultures of enteric bacteria, namely, Salmonella typhimurium (two strains), Listeria monocytogenes (three strains), Proteus mirabilis, Escherichia coli (three strains), and Enterococcus faecalis. Enterocyte viability was assessed using vital dyes, epithelial permeability was measured using transepithelial electrical resistance, enterocyte morphology and bacteria-enterocyte interactions were visualized using light and electron microscopy, and bacterial internalization was assessed using a quantitative culture of lysed enterocytes. RESULTS: B. fragilis enterotoxin did not affect enterocyte viability but decreased transepithelial electrical resistance, and individual enterocytes pulled apart. Enterotoxin pretreatment decreased internalization of L. monocytogenes (P < 0.01) but increased (P < 0.01) internalization of the other strains of enteric bacteria. Augmented bacterial internalization was associated with preferential bacterial adherence on the exposed lateral surface of enterotoxin-treated enterocytes. CONCLUSIONS: B. fragilis enterotoxin was associated with HT-29 cell rounding and with augmented internalization of selected strains of enteric bacteria that were preferentially adherent on the exposed enterocyte lateral surface.

Bacterial Adhesion↗
PubMed1990

Chloride conductance and intracellular chloride accumulation in mouse Peyer's patch enterocytes.

1. Measurements of membrane potential, Cl- conductance and intracellular Cl-, K+, Na+ and H+ activities have been carried out in the follicle-associated epithelium of the mouse Peyer's patch to characterize further the physiological properties of antigen-transporting M cells, enterocytes and intraepithelial lymphocytes. 2. Intraepithelial lymphocytes, identified in random impalements as a second negative jump in membrane potential (Vm), were found to have higher K+ and H+ activities, lower Na+ and Cl- activities and higher negative values for Vm than either of the other two epithelial cell types. Cl- activity in these cells was higher than that predicted from the Nernst equation. 3. M cells identified as having the first negative jump in Vm in impalements involving intraepithelial lymphocytes were unable to accumulate Cl-. They also had a lower Vm than that found in apparently fully differentiated enterocytes. This Vm was partly depolarized at a low Cl- concentration. 4. Apparently fully differentiated enterocytes could be further divided into two populations depending on whether the Vm could or could not be partly depolarized by a low Cl- concentration. The mean Vm and intracellular Cl- activity of Cl(-)-sensitive cells, measured in high Cl- medium, were less than values found for Cl(-)-insensitive enterocytes. Cl- was only accumulated by enterocytes showing no depolarization at low external Cl- concentration. 5. The Vm of mature villus enterocytes was the same as that determined for Cl(-)-insensitive follicle-associated enterocytes. Villus enterocyte Vm was not depolarized at a low Cl- concentration. 6. The present ability to distinguish two apparently large populations of follicle-associated enterocytes having M cell-like or villus enterocyte-like properties is discussed in relation to current theories describing how M cells might be formed. The presence of a Cl- conductance in M cell enterocytes, the inability to accumulate Cl- and the maintenance of a low Vm could aid endocytosis of macromolecules across the apical membrane.

Animals↗
PubMed1998

Cytochalasin-induced actin disruption of polarized enterocytes can augment internalization of bacteria.

Cytochalasin-induced actin disruption has often been associated with decreased bacterial internalization by cultured epithelial cells, although polarized enterocytes have not been systematically studied. In assays using confluent polarized HT-29 enterocytes, cytochalasin D appeared to increase internalization of wild-type Salmonella typhimurium, Proteus mirabilis, and Escherichia coli. HeLa and HEp-2 epithelial cells, as well as HT-29 and Caco-2 enterocytes, were used to clarify this unexpected observation. Resulting data showed that cytochalasin D was associated with increased internalization of S. typhimurium and P. mirabilis by both HT-29 and Caco-2 enterocytes and with increased internalization of E. coli by HT-29 enterocytes; with either HeLa or HEp-2 cells, cytochalasin was associated with no change or a decrease in internalization of these same bacterial strains. Cytochalasin caused decreased internalization of Listeria monocytogenes by HT-29, Caco-2, HeLa, and HEp-2 cells, indicating that cytochalasin did not consistently augment bacterial internalization by polarized enterocytes. Fluorescein-labeled phalloidin confirmed marked disruption of filamentous actin in cytochalasin-treated HT-29, Caco-2, HeLa, and HEp-2 cells. Cytochalasin had no noticeable effect on epithelial viability but caused distorted apical microvilli, cell rounding, and separation of adjacent enterocytes in confluent cultures (with a corresponding decrease in transepithelial electrical resistance). Scanning electron microscopy showed that cytochalasin-induced enhanced bacterial internalization was associated with preferential bacterial adherence on the exposed enterocyte lateral surface. Colchicine, used to disrupt microtubules, had no noticeable effect on bacterial internalization by HT-29 or Caco-2 enterocytes. These data indicated that for HT-29 and Caco-2 enterocytes, cytochalasin-induced disruption of filamentous actin might augment internalization of some bacterial species by a mechanism that appeared to involve exposure of the enterocyte lateral surface.

Actins↗
PubMed2002

Effect of tumor necrosis factor alpha, interferon gamma, and interleukin-4 on bacteria-enterocyte interactions.

BACKGROUND: Little is known about the mechanisms involved in bacterial translocation from the intestinal lumen to extraintestinal sites. Because the cytokine cascade associated with sepsis, inflammation, and trauma has been shown to affect intestinal epithelial permeability, experiments were designed to clarify the effects of selected cytokines on bacterial adherence to and internalization by cultured HT-29 and Caco-2 enterocytes. METHODS: Mature, confluent enterocytes were pretreated 48 to 72 h with tumor necrosis factor alpha (TNF-alpha), interferon gamma, (IFN-gamma), or interleukin-4 (IL-4). Adherence of Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, and Escherichia coli was measured by enzyme-linked immunosorbent assay and bacterial internalization was quantified by the gentamicin protection assay. Enterocyte permeability was measured by transepithelial electrical resistance and by flux of 40-kDa fluorescent dextran. Bacterial transmigration across confluent enterocytes was measured using enterocytes cultivated on permeable supports. RESULTS: TNF-alpha, IFN-gamma, and IL-4 had variable effects on bacterial adherence to HT-29 and Caco-2 enterocytes, although the most consistent finding was increased bacterial adherence associated with INF-gamma. However, none of these cytokines had a noticeable effect on bacterial internalization by either Caco-2 or HT-29 enterocytes. In addition, none of these cytokines had a noticeable effect on the permeability of confluent enterocytes as measured by transepithelial electrical resistance or dextran flux. Bacterial transmigration across confluent HT-29 enterocytes was not altered by TNF-alpha, IFN-gamma, or IL-4; however, IL-4 consistently decreased bacterial transmigration across confluent Caco-2 enterocytes. CONCLUSIONS: IFN-gamma may augment the epithelial adherence of selected species of enteric bacteria, and IL-4 may act as a barrier-sustaining agent to decrease bacterial migration across the intestinal epithelium.

Bacterial Adhesion↗
PubMed1995

Influence of stage of lactation on glucose and glutamine metabolism in isolated enterocytes from dairy cattle.

Pathways of glutamine and glucose metabolism in early-, mid-, and late-lactation dairy cows were evaluated by in vitro incubations of enterocytes for 2 hours with [U-14-C]glutamine and [U-14C]glucose. Enterocytes from early-lactation cows produced greater amounts of CO2 from glutamine in concentrations that ranged from 2 to 8 mmol/L than enterocytes from either mid- or late-lactation cows. Enterocytes from early-lactation cows also produced greater amounts of CO2 from 4 and 6 mmol/L glucose than enterocytes from either mid- or late-lactation cows. Glutamine was metabolized via glutaminolysis mainly to ammonia, alanine, aspartate, glutamate, and CO2, and more of these products were produced in enterocytes from early-lactation cows than from pooled mid- and late-lactation (PML) cows. Glucose was metabolized mainly to lactate, as compared with pyruvate and CO2. Lactate and CO2 production were both greater in enterocytes from early-lactation cows than from PML cows. Glutamine as the sole substrate accounted for all the energy requirements of enterocytes from early-lactation cows but contributed only 31% in the presence of glucose. Similarly, glucose accounted for all the energy requirements of enterocytes from early-lactation cows and contributed 69% in the presence of glutamine. In enterocytes from all cows, the rate of adenosine triphosphate (ATP) production was greater in the presence of both glucose and glutamine compared with that in the presence of either substrate alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗