Conjugated primary bile salts reduce permeability of endotoxin through intestinal epithelial cells and synergize with phosphatidylcholine in suppression of inflammatory cytokine production.
OBJECTIVE
Endotoxemia was shown to be integral in the pathophysiology of obstructive jaundice. In the current study, the role of conjugated primary bile salts (CPBS) and phosphatidylcholine on the permeability of endotoxin through a layer of intestinal epithelial cells and the consequent activation of basolaterally cocultured human mononuclear leukocytes were measured.


METHODS
In a coculture model, a layer of differentiated, confluent Caco-2 cells was apically stimulated with growth-arrested, nonpathogenic Escherichia coli.


METHODS
Basic human cell culture laboratory.


METHODS
The effect of CPBS (0.5 mM and 1.5 mM), phosphatidylcholine (0.38 mM), and human bile (0.5% vol/vol) on the barrier function was assessed by the measurement of transepithelial electrical resistance, by endotoxin permeability through the intestinal epithelial cell layer, and by basolateral cytokine enzyme-linked immunosorbent assay measurement (tumor necrosis factor-[alpha], interleukins-6, -8, and -10). Micelles formed by CPBS were detected by dynamic light scattering. The association of endotoxin with CPBS micelles was tested by fluorescence resonance energy transfer.


RESULTS
Apical addition of CPBS suppressed the permeability of endotoxins through the intestinal epithelial cell layer significantly. In parallel, apical supplementation of CPBS dose-dependently reduced the basolateral production of all cytokines measured. Apical phosphatidylcholine supplementation enhanced this effect significantly. CPBS formed micelles (diameter, 134 +/- 7 nm), which were able to bind endotoxin to their surface.


CONCLUSIONS
CPBS can reduce the permeation of endotoxin through intestinal epithelial cell layers by binding it to micelles. Thereby, the inflammatory processes beyond the mucosal surface are suppressed, an effect that is enhanced by phosphatidylcholine.
Parlesak
Alexandr
A
Nutritional Immunology Group, Biocentrum, Technical University of Denmark, Lyngby, Denmark. alpa@biocentrum.dtu.dk
Schaeckeler
Simone
S
Moser
Lydia
L
Bode
Christiane
C
D001647:Bile Acids and Salts / Q000502:physiology*; D002478:Cells, Cultured; D004731:Endotoxins / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000378:metabolism; D016753:Interleukin-10 / Q000096:biosynthesis*; D015850:Interleukin-6 / Q000096:biosynthesis*; D016209:Interleukin-8 / Q000096:biosynthesis*; D007413:Intestinal Mucosa / Q000166:cytology* / Q000378:metabolism*; D010539:Permeability; D010713:Phosphatidylcholines / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D001647:Bile Acids and Salts; D004731:Endotoxins; D015850:Interleukin-6; D016209:Interleukin-8; D010713:Phosphatidylcholines; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10