Transduction pathways regulating the trophic effects of Saccharomyces boulardii in rat intestinal mucosa.
Saccharomyces boulardii is a probiotic yeast that is widely prescribed in lyophilized form; it determines several effects in human and rat small intestine including endoluminal secretion of enzymes and of polyamines, stimulation of microvillous enzymes, of sIgA, increased production of the receptor for polymeric immunoglobulins by crypt cells, and enhanced d-glucose uptake.


OBJECTIVE
The objective of this study was to determine the pathway(s) by which these effects generated by the yeast are transduced into mucosal cells.


METHODS
Litters of six growing Wistar rats each were treated with S. boulardii (50 microg/gram body weight) or with saline between days 30 and 34 postpartum. For each animal, the cytosol was prepared from the whole mucosa after the fat cake was discarded. Several known intestinal substrates were immunoprecipitated and immunoblotted using specific antibodies recognizing the non-, mono-, or diphosphorylated forms of these substrates. The signals were detected using Echochemiluminoscence (ECL) and were measured by optodensitometry.


RESULTS
Treatment with S. boulardii markedly enhanced the RAS-GAP-RAF-ERK(1,2) pathway with participation of growth receptor bound 2 protein, SHC, SOS, and CRKII. Unit p85alpha of phosphatidylinositol 3 kinase, tested in its phosphorylated form, was also enhanced by the probiotic compared to control samples. In rats treated with an inhibitor of RAF-1 and of ERK(1,2) (PD098059) the expression of mucosal disaccharidases was inhibited by about 50%.


CONCLUSIONS
The probiotic S. boulardii generates in vivo mitogen and metabolic signals that are transduced into intestinal mucosal cells, downstream from the apical membrane to the nuclei, using recruitment substrates and serine, threonine, or tyrosine kinases.
Buts
Jean-Paul
JP
Unit of Pediatric Research, Laboratory of Pediatric Gastroenterology and Nutrition, Faculty of Medicine, Université Catholique de Louvain, Brussels, Belgium. buts@gype.ucl.ac.be
De Keyser
Nadine
N
D000818:Animals; D004186:Disaccharidases / Q000378:metabolism; D007413:Intestinal Mucosa / Q000201:enzymology / Q000378:metabolism / Q000382:microbiology*; D007583:Jejunum / Q000201:enzymology / Q000382:microbiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D050737:Proto-Oncogene Proteins c-crk / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012440:Saccharomyces / Q000502:physiology*; D015398:Signal Transduction; D000097782:NF-kappaB-Inducing Kinase
D004186:Disaccharidases; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D050737:Proto-Oncogene Proteins c-crk; D000097782:NF-kappaB-Inducing Kinase