Cholesteryl esters in human gallbladder bile and mucosa

Carcinoma in situ of the cystic duct

Cholelithiasis and cholesterolosis associated with carcinoma in situ of the cystic duct epithelium was observed in a male patient. Ultrastructurally, small acini-like lined a thickened, reduplicated basal lamina encompassing a pleiomorphic population of cells, including typical cholecystocytes, a poorly differentiated type, and cells containing modified mucous vesicles with heterogeneous fatty deposits. Even though the etiology of this apparent neoplastic epithelium and of its thickened basal lamina is unclear, it is hypothesized to be the result of an altered control of cell adhesion mechanisms, resulting from a repeated renewal of the typical epithelium abraded by the passage of the stones and the biliary sludge, associated with inflammatory stimuli that accompany cholecystolithiasis. Based on recent studies, it is suggested that investigations of molecular markers in extrahepatobiliary tract lesions and retrospective studies of these archival tissues could clarify the association of these neoplastic changes with other hepato-biliary lesions.

Intracellular liposomes and cholesterol deposits in chronic cholecystitis and biliary sludge

Ultrastructural study of a group of selected specimens of chronic cholecystitic gallbladders reveals cholecystocyte changes characterized by abraded and altered microvilli accompanied by mitochondrial damages in the apical regions as well as mucus accumulation with aggregated, angulated lysosomes and heterogeneous liposomes. These liposomes contain needle-like crystals, probably rich in cholesterol. Many fragments of cholecystocystes and damaged organelles or contents can be found in the biliary sludge. These data support previous reports suggesting that there is an association between cholecystitis and the presence of cholelithiasis, subsequent to the production of altered bile. The present data suggest that disintegrating, sloughed cholecystocyte contents also contribute to the bile sludge, a complex milieu enriched by lipids, cholesterol deposits, altered mucus due in part to changes in expression of apomucins. The instability of prolonged storage of such modified bile, caused and/or accompanied by other associated metabolic defects, including gallbladder sluggishness, would favor the nucleation and the enlargement of gallstones. Based on the aforementioned data, a comprehensive sequence for cholecystocyte ultrastructural alterations and pathologies is proposed, as a result of chronic cholecystitis.

Biochemical and morphological correlations in human gallbladder with reference to membrane permeability

There is good evidence that gallbladder epithelium is permeable to a diverse range of molecules which move into the epithelial cell from the lumen or the basement membrane. Morphological investigations have shown both secretory mucous droplets, components of the endocytosis pathway together with evidence of a system allowing passage of molecules across the basement membrane. This indicates that the gallbladder epithelium may be influenced by molecules presented via the apical and basal membranes, complicating our understanding of gallbladder function, particularly in disease. Gallbladder disease increases the proteoglycan content of the basement membrane, but the implication of this in terms of permeability remains to be defined. Indeed, it remains unknown whether this precedes disease or is a manifestation of the disease process. The removal of water from hepatic bile by gallbladder involves two counter ion transport systems. Autoradiography shows that ion transport occurs into the lateral intracellular spaces but it remains unclear whether this leads to a hypertonic solution in these spaces causing an osmotically driven water absorption or if the process involves an osmotically linked isotonic secretion. These ion pumps are reversible, for water is absorbed during the interdigestive phase but fluid is secreted into the lumen during digestion or in the presence of disease. Appropriate neural stimulation can increase or decrease fluid absorption from the lumen while vasoactive intestinal peptide or secretin promote fluid secretion, probably mediated by prostaglandins leading to raised cyclic AMP acting at the cellular level. Immediate control may depend on intracellular Ca2+ which activates a calmodulin-protein kinase, phosphorylating the counter ion transporters to downregulate their activity. Failure of this regulatory process may explain the initial increase in bile concentrating potential seen in the development of gallstones although the mechanism of such failure remains unknown. More concentrated bile increases movement of biliary compounds into gallbladder epithelial cells which alter gallbladder function in a complex manner. Secondary bile acids are raised in gallstone disease and increase permeability of the gallbladder epithelium to molecules including cholesterol. This cholesterol absorbed from the lumen may have paramount importance to gallbladder function. Raised biliary cholesterol reduces gallbladder motility, possibly by increasing the amount of cholesterol in gallbladder muscle membranes and reducing contraction in response to cholecystokinin. However, increased secondary bile acids are also associated with an alteration in phospholipid acyl groups which may alter ion transport activity and/or cholesterol solubility within the micelle/vesicle. As the acyl groups show increased arachidonate levels the production of prostaglandins could be raised, although currently it is not known if this phospholipid arachidonate enters the epithelial cells. In addition, gallbladder inflammation is associated with raised phospholipase A2 activity, leading to formation of fatty acids and lysophospholipid which causes membrane damage. The fatty acids are likely to displace cholesterol from the micelle but may also act directly on the epithelium, possibly increasing prostaglandin production and thus stimulating mucin secretion. Increased mucin secretion is seen early in gallstone disease but the evidence presently available cannot determine if this is a causative factor.

Chromatographic methods in the analysis of cholesterol and related lipids

Methods using thin-layer chromatography, solid-phase extraction, gas chromatography, high-performance liquid chromatography and supercritical fluid chromatography are described for the analysis of single cholesterol, esterified and sulfated cholesterol, and for cholesterol in the context of other lipid components, like other sterols and lipid classes. In connection with these techniques several clinical applications are mentioned.

Cholesterol metabolism in human gallbladder mucosa: relationship to cholesterol gallstone disease and effects of chenodeoxycholic acid and ursodeoxycholic acid treatment

The objective of this study was to investigate cholesterol metabolism in human gallbladder mucosa, especially in relation to hepatic cholesterol metabolism, gallstone disease and treatment with bile acids. Gallbladder mucosa and liver tissue samples were collected in 44 patients undergoing cholecystectomy; 30 had cholesterol gallstones and the rest were stone free. Ten of the gallstone patients were treated with chenodeoxycholic acid and eight received ursodeoxycholic acid, with a daily dose of 15 mg/kg body wt, for 3 wk before surgery. The 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, governing cholesterol synthesis, was considerably lower in the gallbladder mucosa than in liver tissue (28 +/- 6 and 120 +/- 40 pmol/min/mg protein). The acyl coenzyme A:acyltransferase activity in the gallbladder mucosa catalyzing the esterification of cholesterol was, on the other hand, several times higher than corresponding activity in the liver (92 +/- 23 and 11 +/- 2 pmol/min/mg protein). In the presence of exogenous cholesterol, the acyl coenzyme A:acyltransferase activity increased about twofold in the gallbladder mucosa. The acyl coenzyme A:acyltransferase activity of the gallbladder mucosa from untreated gallstone patients was not stimulated further by the addition of exogenous cholesterol. Otherwise, there were no significant differences in acyl coenzyme A:acyltransferase and 3-hydroxy-3-methylglutaryl coenzyme A reductase activities in the gallbladder mucosa of gallstone patients compared with gallstone-free controls. Treatment with chenodeoxycholic and ursodeoxycholic acids did not affect the 3-hydroxy-3-methylglutaryl coenzyme A reductase activity of the gallbladder mucosa but reduced the acyl coenzyme A:acyltransferase activity by 60% to 65%.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of lipid accumulation in the gallbladder mucosa of the ground squirrel fed a lithogenic diet

Richardson's ground squirrels (Spermophilus richardsonii) of both sexes were fed a 2 per cent cholesterol-enriched diet for intervals of 12, 18, and 24 h; 3, 5, and 7 days; and 2, 3, 10, and 20 weeks. It was shown that free (unesterified) cholesterol, phospholipid, and cholesterol ester accumulated in specific regions of the gallbladder mucosa during cholelithiasis. Electron microscopy revealed the presence of lipids inter- and intracellularly as early as 12 h after ingestion. By 7 days, lipids were seen in dilated endoplasmic reticulum, as well as in supranuclear and basal regions of epithelial cells. Histochemical localization revealed free cholesterol in dilated endoplasmic reticulum and residual bodies at the ultrastructural level. Neutral lipid was observed by light microscopy in the supranuclear and basal regions of the cells. In 10- and 20-week treated animals, lipid droplets were also seen in the lamina propria and macrophages. The lesion induced by cholesterol ingestion persisted throughout the experimental period, and while different from that in human tissue, it was similar to those observed in experimental canine cholesterosis.

Strategy for the analysis of steryl esters from plant and animal tissues

Methods are described for the analysis of intact steryl esters present in complex mixtures isolated from plant or animal tissues. A preliminary examination by analytical thin-layer chromatography (TLC) and capillary column gas chromatography-mass spectrometry (GC-MS) under electron impact (EI) ionisation reveals the complexity of the mixture and the nature of the steryl moieties. Preparative TLC is then utilised to separate the steryl esters into two broad groups, containing fatty acyl moieties of shorter (C2-C8) or longer chain length (C10-C22). The shorter-chain fatty acyl steryl esters are separated by adsorption high-performance liquid chromatography (HPLC) on a LiChrosorb Silica-60 column. The steryl esters with longer-chain fatty acyl moieties are analysed by reversed-phase HPLC on either an Ultrasphere ODS, 5-micron, or a S3 Spherisorb ODS, 3-micron, column. Steryl esters with unsaturated fatty acyl moieties are eluted with the shorter-chain fatty acyl steryl esters. The presence of the unsaturated fatty acyl esters can be monitored by analytical argentation TLC, which will also reveal the degree of unsaturation. The steryl esters are fractionated into the saturated, mono-, di-, tri- and polyene acyl types by preparative medium-pressure liquid chromatography on a column of 10% AgNO3-silica gel. Each of these steryl ester types can then be resubmitted to reversed-phase HPLC or analysed by GC-MS on a short fused-silica capillary column with a bonded phase of the OV-1 type. GC-MS on a magnetic-sector instrument under negative-ion chemical ionisation conditions with ammonia as the reagent gas produces fragment ions for both the steryl and fatty acyl moieties, thus permitting identification of the individual intact steryl esters. These various methods are illustrated by analyses of the steryl ester mixtures obtained from human plasma, barley seedlings, palm oil and rape seed oil.

Capillary gas chromatography/mass spectrometry of cholesteryl esters with negative ammonia chemical ionization

Mixtures of both synthetic and naturally occurring (human plasma cholesteryl esters have been examined by capillary gas chromatography/mass spectrometry (GC/MS). A magnetic sector mass spectrometer was used and a variety of ionization modes were assessed with a view to obtaining structural information on intact cholesteryl esters. By employing ammonia as reagent gas, with negative ion scanning, spectra were produced from which the nature of steryl and fatty acyl moieties could be readily deduced. Analyses were performed at an ion source temperature of 300 degrees C in order to maintain the integrity of the gas chromatographic profile. The technique described is of general use for the GC/MS analysis of steryl esters, particularly in conjunction with magnetic sector instruments.

Lipid in the human gallbladder mucosa. A histochemical study by light and electron microscopy

The distribution of lipids in the epithelium of 70 gallbladders removed for cholecystitis was investigated histochemically. Lipid was demonstrated in 68 gallbladders--cholesterol and its esters, triglycerides, free fatty acids and phospholipids. Neutral lipid was found at the bases of epithelial cells in 90 per cent and at the apex in 10 per cent of the gallbladders. Phospholipid was shown at the apex of epithelial cells in 64 per cent of the gallbladders. Electron microscopy in 12 specimens revealed cholesterol in and between the epithelial cells and in the underlying connective tissue.