부산대학교 도서관

Previous studies indicate that certain probiotic bacterial strains or their soluble products can alleviate proinflammatory cytokine secretion by intestinal epithelial cells (IEC), but their impact on epithelial chloride ([Cl.sup.-]) secretion remains elusive. To further decipher the mechanisms of the cross-talk between bacteria/soluble factors and epithelial cells, we analyzed the capacity of the probiotic strain Bifidobacterium breve C50 (Bb C50), its conditioned medium, and other commensal Gram (+) bacteria to modulate epithelial [Cl.sup.-] secretion. The effect of Bb C50 on carbachol- (CCh) or forskolin (Fsk)-induced [Cl.sup.-] secretion was measured in an IEC line in Ussing chambers. The mechanisms involved in the regulation of [Cl.sup.-] secretion were assessed by measuring intracellular [Ca.sup.2+] concentration, phosphatase activity, protein kinase (PK) C and PKA activation, and cystic fibrosis transmembrane conductance regulator (CFTR) expression. CCh- or Fsk-induced [Cl.sup.-] secretion [short-circuit current (Isc): 151 [+ or -] 28 and 98 [+ or -] 14 [micro]A/[cm.sup.2], respectively] was inhibited dose-dependently by Bb C50 (Isc 33 [+ or -] 12 and 49 [+ or -] 7 [micro]A/[cm.sup.2] at multiplicity of infection 100; P < 0.02). Fsk-induced [Cl.sup.-] secretion was also inhibited by Lactobacillus rhamnosus 10893. No other inhibitory effect was recorded with the other Gram (+) bacteria tested. The inhibitory effect of Bb C50 on CCh-induced [Cl.sup.-] secretion targeted a step downstream of epithelial [Ca.sup.2+] mobilization and was associated with decreased PKC activity. Thus, Bb C50 and secreted soluble factors, by inhibiting phosphorylation processes, may promote intestinal homeostasis by controlling [Cl.sup.-] secretion. J. Nutr. 140: 7-11, 2010. doi: 10.3945/jn.109.114553.