Lipopolysaccharide From Escherichia Coli Stimulates Mucin Secretion by Cultured Dog Gallbladder Epithelial Cells

Abstract

Biliary infection is associated with mucin hypersecretion by the biliary epithelium. Mucins have been identified as potent pronucleators of cholesterol in bile. The aim of the present study was to determine whether lipopolysaccharides (LPS) from different bacteria are capable of stimulating mucin secretion by cultured dog gallbladder epithelial (DGBE) cells, and to investigate the mechanism by which LPS stimulate mucin secretion. Mucin secretion by confluent monolayers of DGBE cells was quantified by measuring the secretion of [3H]-N-acetyl-D-glucosamine-labeled glycoproteins. Cell viability was evaluated by measuring the leakage of the enzyme, lactate dehydrogenase (LDH), into the culture medium. LPS, derived from Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa (200 g/mL), all caused an increase in mucin secretion by the DGBE cells, without causing concomitant cell lysis. LPS from E. coli was found to be the most potent stimulator of mucin secretion, and increased mucin secretion by the DGBE cells to 252% ؎ 14% of control. LPS from E. coli had no effect on intracellular cyclic adenosine monophosphate (cAMP) levels in the DGBE cells. Addition of the nitric oxide (NO)-releasing compound, NOR-4 (0.125-1 mmol/L), to the cells did not result in increased mucin secretion, and the NO synthase inhibitor, N -nitro-L-arginine methyl ester (L-NAME) (4 or 10 mmol/L), did not inhibit the LPSstimulated mucin secretion. Exogenous tumor necrosis factor ␣ (TNF-␣) (1-10 ng/mL) did cause a minor increase in mucin secretion by the DGBE cells, but the effect of LPS from E. coli on mucin secretion could not be inhibited by preincubation with a TNF-␣ antibody (10 g/mL). We conclude that LPS stimulates mucin secretion by the gallbladder epithelium. Whether this stimulation is mediated by TNF-␣ remains to be determined. (HEPATOLOGY 1999;29:1352-1357.)Gallbladder mucin, the primary glycoprotein secreted by the gallbladder, is a densely glycosylated macromolecule with a molecular mass of approximately 2 ϫ 10 6 d. Mucin is regarded as an important contributing factor to gallstone formation. [1][2][3] Mucin has been shown to be present in the nucleus of several types of gallstones, and a macromolecular complex of mucin and bilirubin has been identified as a major structural component of the gallstone matrix. 4,5 Purified human gallbladder mucin is capable of nucleating cholesterol crystals from human bile. 6 Gallbladder mucus hypersecretion and increased mucin concentration are common findings in nearly all animal models of cholesterol gallstone disease. Mucin hypersecretion precedes crystal or stone formation. 7,8 These findings suggest that increased mucin secretion plays a role in the initial stages of gallstone formation.We have reported the succesful long-term culturing and passaging of normal, well-differentiated gallbladder epithelial cells from the dog. 9 These cells form electrically leakproof monolayers and synthesize protein and mucous glycoprotein. They have been extensively studied with regard to water and ...

Gallbladder Epithelium as a Niche for Chronic Salmonella Carriage

“…We demonstrated that in vitro, Salmonella infection of polarized gallbladder epithelial cells corroborates in vivo mouse model findings and thus represents a good model for host-pathogen interaction studies. These DGEC have been intensively used for physiological studies, which supported their use as a model for human gallbladder epithelial cells (24)(25)(26)(27)(28)(29). The percentage of S. Typhimurium invasion obtained in this study is relatively lower than results of other studies with polarized epithelial (30)(31)(32).…”

MUC5AC, a Gel-Forming Mucin Accumulating in Gallstone Disease, Is Overproduced via an Epidermal Growth Factor Receptor Pathway in the Human Gallbladder

“…It has been reported on the basis of Northern blot analysis that TNF-␣ increased MUC5AC expression in murine intrahepatic biliary epithelial cells. 19 Conversely, TNF-␣ was shown to have little or no effect on mucin secretion in dog gallbladder epithelial cells 37 and on MUC5AC expression in intestinal cells. 50 Likewise, we found here that TNF-␣ alone had only a minor effect on MUC5AC production in the gallbladder.…”

Roles ofVibrio fischeriand Nonsymbiotic Bacteria in the Dynamics of Mucus Secretion during Symbiont Colonization of theEuprymna scolopesLight Organ

“…In the lungs of patients suffering from cystic fibrosis, excess mucus secretion leads to creation of an environment that is conducive to persistent colonization by Pseudomonas aeruginosa (5,27). Further studies of this association and others have shown that bacterial lipopolysaccharide (LPS), a component of the outer membrane of gram-negative bacteria, is capable of upregulating genes involved in mucin synthesis (12,25) and inducing mucus secretion (8).…”