Effects of perorally applied endotoxin on colonic mucins of germfree rats.
BACKGROUND
The intestinal epithelium, with the potential to restrict luminal noxae from the host, secretes a mucous layer with various protective functions. Microbial colonization of germfree (GF) rats stimulates this mucin-secreting tissue. The present study determined the effect of bacterial lipopolysaccharides (LPS) on this process.


METHODS
One, 3, and 5 days after peroral application of 35 micrograms LPS/100 g body weight (from Escherichia coli O55:B5), LPS concentrations were monitored in ingesta, intestinal tissue, and liver. Mucin high molecular weight glycoproteins (HMG), released in response to LPS, were isolated and separated into mucins, i) attached to the colonic epithelium (EM) and ii) mixed to the luminal content (LM), respectively. Subsequently, the binding capacity of both mucin fractions for various lectins and for type-1 pili expressing E. coli was determined.


RESULTS
Ingesta and tissue had maximal LPS concentrations on days 3 (jejunum) and 5 (colon). Maximal EM secretion was found on day 3, release of LM further increased to day 5. Both mucin fractions had altered glycosylation patterns: augmentation of beta-galactose, alpha-N-acetyl galactosamine, and mannose coincided with a decrease in alpha-fucose. Compared with the controls, attachment of E. coli to EM increased slightly on day 1 only; the binding capacity of LM increased continuously up to day 5.


CONCLUSIONS
Results suggest that mucins, released in response to LPS, in addition to the epithelial protection, support the gut microbial clearance system.
Dept. for Laboratory Animal Science and Animal Facility, Medical School Hanover, Germany.
M L
ML
Enss
H
H
Müller
U
U
Schmidt-Wittig
R
R
Kownatzki
M
M
Coenen
H J
HJ
Hedrich
D000284:Administration, Oral; D000818:Animals; D001422:Bacterial Adhesion; D003106:Colon / Q000378:metabolism*; D004926:Escherichia coli; D005856:Germ-Free Life; D006023:Glycoproteins / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D037102:Lectins / Q000378:metabolism; D008070:Lipopolysaccharides / Q000008:administration & dosage*; D008297:Male; D009077:Mucins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D006023:Glycoproteins; D037102:Lectins; D008070:Lipopolysaccharides; D009077:Mucins