Effect of Saccharomyces boulardii on cAMP- and Ca2+-dependent Cl- secretion in T84 cells

Several reports have confirmed that the cooperative interaction between cAM P- and Ca2+-mediated transduction pathways may contribute to the stimulator y or inhibitory regulation of Cl- secretion in intestinal epithelium. Sacch aromyces boulardii has been shown to inhibit cholera toxin-induced secretio n in rat jejunum. We have identified a 120-kDa protein in medium conditione d by Saccharomyces boulardii that reduces cholera toxin-induced cAMP in int estinal cells. The present study evaluated the effect of medium conditioned by Saccharomyces boulardii on cAMP- and Ca2+-mediated Cl- secretion in T84 cells. Experiments performed with cAMP agonists revealed that 1 hr of prei ncubation of cells with medium conditioned by Saccharomyces boulardii was n ecessary to elicit a 40-50% reduction in receptor (cholera toxin, prostagla ndin E-2, and vasoactive intestinal polypeptide) and nonreceptor (forskolin ) mediated cAMP synthesis and I-125(-) efflux. Secretion induced by carbach ol was inhibited when cells were pretreated for 1 hr with medium conditione d by Saccharomyces boulardii despite the absence of inhibition of Ins (1,4, 5)P-3. From this study we conclude that Saccharomyces boulardii exerts an i nhibitory effect in vitro on Cl- secretion mediated through both cAMP- and Ca2+-mediated signaling pathways.