-
Journal of Surgical Research 02/2010; 158(2):414. · 2.25 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Little is known about the mechanisms involved in bacterial translocation from the intestinal lumen to extraintestinal sites. Because Staphylococcus aureus can colonize the intestinal tract, and because the intestinal tract is a reservoir for antibiotic resistant S. aureus, experiments were designed to clarify the interactions of S. aureus with cultured intestinal epithelial cells, and assays included measurements of bacterial internalization, enterocyte apoptosis, and epithelial barrier function.
Mature, confluent enterocytes were incubated 1 h with S. aureus, and the gentamicin protection assay was used to quantify intracellular bacterial survival at various time intervals up to 120 h later. Enterocyte apoptosis was assessed using Annexin V, and the permeability of confluent enterocyte cultures was measured by transepithelial electrical resistance and by transmigration of Escherichia coli across confluent enterocytes.S. aureus was internalized by cultured enterocytes and remained viable for up to 120 h within both HT-29 and Caco-2 enterocytes. S. aureus intracellular survival was associated with enterocyte apoptosis and with decreased transepithelial electrical resistance across confluent Caco-2 enterocytes. S. aureus intracellular survival over time was also associated with increased E. coli transmigration across confluent Caco-2, but not HT-29, enterocytes.
S. aureus appeared to survive within cultured enterocytes for prolonged time periods, up to several days. Survival of S. aureus within host eukaryotic cells, such as enterocytes, might facilitate persistence of S. aureus in infected tissue despite appropriate antibiotic therapy.
Journal of Surgical Research 10/2003; 114(1):42-9. · 2.25 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
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.
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.
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.
Journal of Surgical Research 06/2002; 104(2):88-94. · 2.25 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
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.
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.
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.
Journal of Surgical Research 07/2001; 98(2):116-22. · 2.25 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The treatment of acute liver failure has evolved to the current concept of hybrid bioartificial liver (BAL) support, because wholly artificial systems have not proved efficacious. BAL devices are still in their infancy. The properties that these devices must possess are unclear because of our lack of understanding of the pathophysiology of liver failure. The considerations that attend the development of BAL devices are herein reviewed. These considerations include choice of cellular component, choice of membrane component, and choice of BAL system configuration. Mass transfer efficiency plays a role in the design of BAL devices, but the complexity of the systems renders detailed mass transfer analysis difficult. BAL devices based on hollow-fiber bioreactors currently show the most promise, and available results are reviewed herein. BAL treatment is designed to support patients with acute liver failure until an organ becomes available for transplantation. The results obtained to date, in this relatively young field, point to a bright future. The risks of using xenogeneic treatments have yet to be defined. Finally, the experience gained from the past and current BAL systems can be used as a basis for improvement of future BAL technology.
Annual Review of Biomedical Engineering 02/2000; 2:607-32. · 12.21 Impact Factor
