BACKGROUND & AIMS: The cellular mechanisms that regulate biliary mucin secretion in humans are unknown. To address this question, human gallbladder epithelial cells were used in primary culture. METHODS: [1-(14)C]-glucosamine-labeled glycoproteins secreted in vitro were analyzed and quantified after exposing cells to activators and inhibitors of the main transduction pathways and to potential biologically active secretagogues. RESULTS: Secreted glycoproteins showed characteristics of biliary mucins. Activators of adenosine 3',5'-cyclic monophosphate-dependent pathway as well as secretin and vasoactive intestinal polypeptide did not significantly modify mucin secretion. By contrast, ionomycin and phorbol-12-myristate 13-acetate increased mucin secretion by 292% +/- 48% and 134% +/- 19% over basal level, respectively. The effects of these two agents were additive and were mediated by a calcium-dependent pathway implicating Ca2+/calmodulin-dependent protein kinase II (Ca2+/CaM-kinase II) and by the activation of protein kinase C (PKC), respectively, as ascertained by using inhibitors. Mucin secretion was stimulated by extracellular adenosine 5'-triphosphate via P2U receptors, cytosolic calcium increase, and PKC and by taurochenodeoxycholate via cytosolic calcium increase and Ca2+/CaM-kinase II. CONCLUSIONS: Mucin secretion in human gallbladder is regulated predominantly by calcium-dependent pathways implicating Ca2+/CaM-kinase II and PKC. Extracellular adenosine 5'-triphosphate and taurochenodeoxycholate may play a role in the regulation of biliary mucin secretion by activating these different signaling pathways.
BACKGROUND & AIMS: The cellular mechanisms that regulate biliary mucin secretion in humans are unknown. To address this question, human gallbladder epithelial cells were used in primary culture. METHODS:[1-(14)C]-glucosamine-labeled glycoproteins secreted in vitro were analyzed and quantified after exposing cells to activators and inhibitors of the main transduction pathways and to potential biologically active secretagogues. RESULTS: Secreted glycoproteins showed characteristics of biliary mucins. Activators of adenosine 3',5'-cyclic monophosphate-dependent pathway as well as secretin and vasoactive intestinal polypeptide did not significantly modify mucin secretion. By contrast, ionomycin and phorbol-12-myristate 13-acetate increased mucin secretion by 292% +/- 48% and 134% +/- 19% over basal level, respectively. The effects of these two agents were additive and were mediated by a calcium-dependent pathway implicating Ca2+/calmodulin-dependent protein kinase II (Ca2+/CaM-kinase II) and by the activation of protein kinase C (PKC), respectively, as ascertained by using inhibitors. Mucin secretion was stimulated by extracellular adenosine 5'-triphosphate via P2U receptors, cytosolic calcium increase, and PKC and by taurochenodeoxycholate via cytosolic calcium increase and Ca2+/CaM-kinase II. CONCLUSIONS:Mucin secretion in human gallbladder is regulated predominantly by calcium-dependent pathways implicating Ca2+/CaM-kinase II and PKC. Extracellular adenosine 5'-triphosphate and taurochenodeoxycholate may play a role in the regulation of biliary mucin secretion by activating these different signaling pathways.
Authors: Laetitia Finzi; Véronique Barbu; Pierre-Regis Burgel; Martine Mergey; Kimberly S Kirkwood; Elizabeth C Wick; Jean-Yves Scoazec; Frédérique Peschaud; François Paye; Jay A Nadel; Chantal Housset Journal: Am J Pathol Date: 2006-12 Impact factor: 4.307
Authors: Nazzareno Ballatori; Na Li; Fang Fang; James L Boyer; Whitney V Christian; Christine L Hammond Journal: Front Biosci (Landmark Ed) Date: 2009-01-01