The study of ethanol effects on intracellular transport and membrane biogenesis in rat hepatocytes revealed that, during synthesis of transport vesicles, the cytosolic phosphatidylinositol 3-kinase incorporated into the membrane of Golgi transport vesicles and a portion of the vesicular phosphatidylinositol was phosphorylated to phosphatidylinositol 3-phosphate. Association of the enzyme with Golgi transport vesicles and the transport to the apical portion of the cell membrane was not affected by 0 to 120 mM ethanol, but was dependent on the presence of the p85 subunit of the phosphatidylinositol 3-kinase. In the presence of ATP-enriched cytosol and calcium ions, association of Golgi transport vesicles with the apical membrane was followed by phospholipase A2-specific hydrolysis of phosphatidylinositol 3-phosphate and incorporation of the transport vesicle membrane into the apical membrane. Association of Golgi transport vesicles with apical membranes was not affected by preincubation of the cell membrane or Golgi transport vesicles with 0 to 120 mM ethanol, but was inhibited when the p85 phosphatidylinositol 3-kinase was incorporated into the membrane before incubation with Golgi transport vesicles. The fusion of Golgi transport vesicles with the apical membrane and generation of lysophosphatidylinositol 3-phosphate and arachidonate was inhibited with EGTA or after depletion of ATP from cytosol. Results of these studies provide evidence that phosphatidylinositol 3-kinase and phospholipase A2 activities are crucial for the final step of exocytotic transport. The process consists of two stages. First, the p85 subunit of phosphatidylinositol 3-kinase is involved in the specific association of the vesicle with membrane receptor, and that is followed by phospholipase A2-specific lysophospholipid generation, perturbation of the membranes, and fusion of the transport vesicle membrane with the apical membrane. Addition of ethanol to the in vitro transport system decreased production of Golgi transport vesicles, but had no effect on their association with apical membrane or fusion with the membrane.
Our findings provide new insights into the mechanism of gastric injury caused by NSAIDs and show that ebrotidine protection against indomethacin-induced mucosal damage occurs through the inhibition of epithelial cell apoptosis triggered by the enhancement in the mucosal TNF-alpha expression. Our data also show that omeprazole does not possess antiapoptotic properties.
Seven individual glycolipids (I -VII) have been isolated from the lipid extract of human saliva. All glycolipids contained glucose, glyceryl ethers and fatty acids, and differed from each other primarily with respect to the number of glucose residues. In addition, glycolipid V contained also the sulfate ester group. The structures of these glycolipids were identified by partial acid and alkaline hydrolysis, oxidation with periodate and chromium trioxide and methylation studies, as :. Diglyceride portion of these compounds consists of 1 -O-alkyl-2-O-acyl-glycerol with the docosanoate and glyceryl-monodocosyl being the predominant acyl and alkyl components.The oral, bronchial, pulmonary, gastrointestinal and reproductive tracts of higher animals secrete viscous mucus which functions mainly as lubricant and protective agent. The viscous properties of the mucous secretions are the result of the presence of high molecular weight glycoproteins called mucins. Until now, it was assumed that both mucous glycoproteins and glycolipids are similar to, or possibly derived from, those found on the cell surfaces [l]. Studies on glycolipids of the salivary glands [2,3] and the mucosa of the gastrointestinal tract [4 -91 indicate that these compounds are of glycosphingolipid nature. Our recent investigations on glycolipids of the human gastric secretion [ 10 -131 showed that these substances are composed of monoalkyl-monoacyl-glycerol and variable number of glucose residues.Since glycoproteins of the saliva and gastric secretion bear considerable structural and immunological similarities [14, 151, it was interesting to learn if the glycolipids of the saliva resemble those of the gastric secretion. Here, we describe the isolation and characterization of the glycolipids present in the human saliva.
EXPERIMENTAL PROCEDURE
MaterialsSaliva was collected from the laboratory personnel into the glass beaker placed in ice bath. Prior to collection the oral cavity of each individual involved was thoroughly rinsed with water. During sampling, care was taken to avoid the obvious contamination of saliva with nasal and bronchial secretions. The saliva was subsequently stored at -20 "C and thawed out immediately before use. Alkyl-1 -chlorides were obtained from the authentic glyceryl ethers by BCl, treatment [ 161. Alkoxyacetaldehydes were prepared from glyceryl-1 -0-alkyl standards by oxidation with periodate [I I]. Methyl ethers of glucose were from the same source as reported [ 171 and were also prepared by methylation of lactose, glucose 6-sulfate and gentiobiose [I 81. Glycosylceramides were prepared from hog gastric mucosa [19] and glyceroglucolipids from human gastric secretion [ 12,131.
Our findings demonstrate that H. pylori lipopolysaccharide can cause gastric mucosal responses typical of acute gastritis and identify the lipopolysaccharide as a virulence factor responsible for the induction of gastric epithelial cell apoptosis by H. pylori.
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